Windy Wellington is renowned for its challenging weather and steep topography, so you wouldn't think anyone would be daft enough to build a house on a cliff edge and rely solely on the sun to heat it. But one daring young couple are doing just that. (SIGHS) Captions were made with the support of NZ On Air. www.able.co.nz Copyright Able 2018 (JOVIAL ORCHESTRAL MUSIC) (TUI CHIRPS) Wellington is my hometown. It's an exciting mix of dramatic landscape and human endeavour, with high, windy hills that have challenged generations of architects and home buyers. After six years working overseas, Karl and Amelie came home to Wellington with a good sized house deposit and their baby, Claudie, in a backpack. Karl works in sustainable building and Amelie in energy efficiency. They had their hearts set on a classic inner suburbs villa. Instead, they found themselves living in a granny flat behind Amelie's mum and dad's house, watching property prices rise out of their reach. Should we do the puzzle? Can Mum help? Shall we start again, bub? Like, we never really thought it was gonna be possible or in the realm of possibility to build our own house. It was always thinking, 'We're just gonna buy a cute little villa and that'll be that; 'that'll be a great first home.' The big truck. At a certain point, I think we put an offer on a house for over 700. But then we rapidly realised that we were still getting a pretty old villa that needed a lot of work. So instead of buying something old, draughty and damp, they started dreaming about building an energy-efficient house warmed by the sun. I don't wanna be cold inside my house. I don't wanna have cold feet. I don't wanna have to wear, you know, woollen jerseys all the time through winter. That's probably the biggest goal that I have. Oh, yeah, it's yours. They knew they had the skills to build a warm green home on a budget, but affordable sections close to town are like hens' teeth, and it felt like they were gonna be in a granny flat forever. (PENSIVE MUSIC) 'Then, after months of searching, they found a block of land in Wadestown. 'It was the right price, got the right amount of sun and was cycling distance from town. 'There was just one problem.' Looks suitably intrepid for Wellington. Don't know if the average person would build here, though. 'The site has already beaten two previous owners because it's so inaccessible. 'It's down such a steep bank, 'the easiest way to get there is down the neighbours' driveway. 'But that only gets you halfway. 'This is crazy Wellington, 'and I know from experience how hard it's gonna be to get tools, building supplies 'and machinery down here, let alone the groceries, once they move in. 'A section this hard to get to must have been the right price.' Hey, guys. Boy. You're tigers for punishment. Nice to see you. How you going? Nice to see you too. Hi. How are you? Wow. What a cracker! How did you find this place? This place is in our neighbourhood, and we just came across it. Karl has a good friend who's an architect who came to look at the site. They didn't say it was mad? I mean` Well, they did say it was mad, but they said it was doable. And why wait till we're older to build our first house? Why not do it now while we have the energy? I think that's awesome. I couldn't agree more. And we're also not shying away from the fact that we're just gonna walk up the stairs. And it probably would be a deal-breaker for most people, and it's one of the reasons why we actually got the site at a relatively affordable price. What's affordable? What was...? Uh, we got it below RV. So we got it for $180,000,... OK. That's OK. ...and the RV IS $200,000. So what have you got planned? A very simple form. Basically a rectangular building on an east-west access, facing the sun so we get lots of that solar energy. The house facing the sun is critical to Karl and Amelie's ingenious greenhouse design. Downstairs, a polished concrete slab works as a massive battery to store the sun's heat. To maximise this passive solar energy, windows cover almost half the north face. The living space is open plan with built-in timber furniture and a stylish kitchen island. Stairs to the top floor find a corridor opening to three bedrooms and two bathrooms. A top deck running the length of the northern face is carefully designed to let winter sun in but provide shade at the height of summer. The house will be airtight and heavily insulated to prevent heat escaping ` a key part of Karl's dream of a house that takes all its warmth from the sun. Capped with a gently pitched roof that collects drinking water, it's a bold, modern house with striking lines that set it out amongst the trees on a steep Wellington hillside. OK, so, great ambitions for the house, but, you know, it's an incredibly steep site. How are you dealing with outside space? We're gonna have a strip of balcony, or deck, and also a green lawn. A lawn? A lawn on a site like this? We wanted the Kiwi requirement on indoor-outdoor flow. So what's your budget for the build? Our budget is $400,000 for construction. And that includes foundations ` everything? Everything. Sounds great, but, you know, I can hear it already. You know, beautiful ` that costs money. Sustainable ` that costs money. Steps, right ` that costs money. When we have cost blowouts, what gives? Well, I think we've designed a house that's not enormous. That's already a huge` Well, it's gonna shrink. (LAUGHTER) It's 140m2, so it's a sensible size. So are you guys rolling your sleeves up as well? Yep. So I'll be building about three days a week. Um, so I've got one day a week off of my normal job. Wow. I would like to do more of that. We do have an 18 month old, so... There's a challenge. ...can't be as hands on as I'd like to be. The other thing that intrigues me is this fascination with sustainability. How far are you taking all these ideas? So we are aiming for a Homestar rating, and we're aiming for an 8 star rating. 8?! Your average house, your average code house in New Zealand is 3 or 4. Wow. Sounding really impressive. Yeah. If they can achieve the 8 star rating, Karl and Amelie's house will be twice as green as the average New Zealand house. (DISTANT KNOCKING) But you don't get any points for building it yourself or employing family members, which is a shame, because Karl's father, Max, is a builder, and Karl's asked him to put off his retirement to build one last house. Oh, well, I was chuffed. And, um, then I went down there and looked over the site and said, 'I'm goin' home.' (LAUGHS) But then, when I went down the site, it's beautiful, you know? A lovely section. Karl's love of the environment started early, growing up on the family's lifestyle block here in Taipa in the Far North. He was really young when he first came here, and this really was his life till he was 18. (BIRDS CHIRP) It was paradise. He lived on a little small block. There's a river there they went fishing. Summer, they swam in it. So there was always this interest in how you live your life and what you do. Even from an early age, Karl was expected to get stuck in and help. He helped build, you know, three of these buildings here, really. He started pretty early, really. So he was 2 there. Because I remember I made the pouch, and we bought the hammer for his 2nd birthday. Oh, OK. He was only about 12 or 13 there. Yeah. Those were the overalls I used. Your overalls. (LAUGHS) For a retiring builder used to straightforward wooden houses, I wonder if Karl and Amelie's high-performing home will be a bit of a challenge. I guess if it's the last house I'm ever gonna build, this is, um... It's quite a nice, interesting job. There's no doubt about that. (BOAT HORN HONKS) (CHIRPS) One of the biggest challenges with this site is getting things down to it, and Karl's kicking off this greenhouse build by doing the least green thing you can think of ` hiring a helicopter to get the digger in and back out again. Of course, it's not just the environmental cost. The inaccessible site may have been a bargain, but this is an expensive way to kick off the build. If they need a helicopter today, how on Earth are they going to get other heavy building materials down there? Choppers are thirsty, but it takes a helicopter just a few minutes when a digger would've taken about four days to get in and out. It's an easy equation, though I suspect making the decision kept Karl awake at night. To get that 8-star rating, any energy used today will need to be balanced out later in the project. The most expensive two minutes of my life. (CURIOUS MUSIC) Really, really good feeling to see that earth being moved around now, and... I never thought I'd be dropping a digger in with a helicopter, but... there you go. And Max is onsite today after a 12-hour journey down from the Far North ` the first of many to come. Dad is the builder on the project. It's the last house he's going to build... he thinks. Um... You know, I wouldn't want anybody else to build it, and we were just lucky enough to get there before he retires, basically. Not every father and son would be able to work together, but Karl and Max have had a lot of practice. So there was a few rough years there where I was a grumpy teenager, and we didn't get on always that well on the building site, but, you know, we've got past that now. It'll be fine. I mean, there's always friction, but I think we're pretty fortunate. We work pretty well together. We grump at each other and get over it and keep working, really. But Max has a long way to travel for what could be a difficult build far from home, and I reckon Karl's energy efficiency ambitions are going to challenge them both. (REFLECTIVE PIANO MUSIC) After two months getting the site ready, the concrete trucks are lining up to pour the all important slab on Karl and Amelie's Wellington hillside section. There's a new set of stairs up to the road, but they're not going to help today. Again, the inaccessible site is causing problems. A very long hose is the answer, but it's not plain sailing. The complexity was that` is it gets blocked, and the pumping trucks most often would rather pump concrete uphill, because it doesn't get air pockets in it. When it goes downhill, it gets air pockets and it can block, and then you've gotta take the pipes apart, get the air out, and that's happened a few of the other times that we've pumped. And it's not just the concrete that's come a long way. We drove down yesterday in a straight run, and that's, like, 12 hours' drive. So that's quite a way. And we brought, you know` Of course, we brought down pumpkins and kumaras and potatoes and half a cow. (LAUGHS) So the car drove like a paper bag, I should tell ya. Whoo-hoo! Two weeks ago, we poured the foundations. That's all of the structural element. And then above that, we have a floating slab, which is sitting on 50ml of ClimaFoam insulation. This is no ordinary slab. It's designed as a big heat battery, storing the warm energy of the sun and radiating it back into the home, rather than out through the walls or ground. So theoretically, they won't have to spend anything on heating. Now the build's underway, Karl's builder mate, Tim, is coming on full-time. Easy. I got the light end. He'll be working with Max when Karl's at work and Karl when Max is back up north for much needed R&R. MAX: It's a bigger job than I thought ` there's no doubt about that ` mainly cos of the insulation. Cos, like, the footing, you look at it and think it's just an ordinary footing. But because we had to float all the boxing, um, up off the floor so it was all fly, it just took a lot longer. All that insulation means the floating slab is thermally broken so that no part of the slab touches the walls or ground. This stops heat escaping to keep out cold and damp. The idea behind Karl and Amelie's concrete slab is this. Imagine the blowtorch as the sun and the pizza stone as the slab. In the same way that this pizza stone should stay hot enough to cook this egg,... (SHELL CRACKS) ...Karl and Amelie's concrete slab should stay warm enough to heat their home. But what happens in winter, when it's only 6 degrees outside, it's blowing and there's no sun? And that's the difference between Karl's ambitious insulation goal in the house they were inspired by. Karl and Amelie's house is a scaled up, heat-efficient version of the award-winning Dog Box in Whanganui. The Dog Box was self built by a group of young architects who wanted to experience construction first-hand. One of that group who still lives in the house is Karl and Amelie's architect, Ben Mitchell-Anyon. Gidday, Ben. Gidday. How are you? Good, man. Who's this? This is Milo. Embracing a steep and very cheap site and using budget building materials, the Dog Box is a mini masterpiece. Its design is so refreshingly simple, the upstairs hallway is out in the open air. Wow. What a great space. Welcome to the hallway. It's lovely. Yeah. So it's completely outside, but we have 2.5m of roof. Generally, the rain doesn't come inside. And then the bath. The bath, yeah. What a great spot to have a bath. And then,... in the western sun, you can crack this open. Oh my goodness! Wow. (LAUGHS) Pretty good, isn't it? Fabulous. At just over half the size of Karl and Amelie's, the 88m2 Dog Box could almost be a trial run for their bigger Wellington home. Oh, nice. We took aspects of this house and translated it into a larger family home that was more suited to the Wellington climate than here. You know, we set out to do all of the simple low-cost things ` orientation; glazing on the right places; eves; thermal mass; and insulation. But Karl's kind of brought this other layer, so I'm really looking forward to seeing what the difference is. Karl's other layer is a level of insulation that's made him so confident his house will heat itself, he's crossed the wood burner off his plans before even the walls are up. (JOVIAL MUSIC) Wellington's sometimes described as a village, and today that village is coming to help shift over 700 concrete blocks down to the building site, where they'll be used to build the back wall of the house. Karl's been calling in favours, but on a wet Saturday morning, he'll be hoping his friends and family turn up. Amelie's father won't be able to keep this up on his own. I'm not sure if I continue to` to take two down. The brand-new stairs are ready for dozens of feet, but luckily the blocks are being dropped at the end of the neighbour's driveway, so we won't have to carry them all the way down from the road. Ooh, boy. This looks like hard work. Supposedly I'm supposed to have some muscles. This looks very busy. It is. Gidday, Chris. How you going? Hi, Karl. Good to see you. You're a bit late. Just a bit. (LAUGHS) We've already moved six of the blocks, but here's some gloves. Let's get going. Ooh, this looks serious. It is. You wouldn't think passing 700 blocks down the stairs would be fun, but it's a good morning's workout and marvellously efficient. This is a lot faster than... Mm. Karl: We need a few more peeps down the stairs. How many people have you got on the job today? Uh, well, we actually haven't had a count up, but I'd tell you we're at about 20 odd right now. How on Earth did you manage to rope all these guys in? Well, a lot of them hadn't been to the site yet, so they didn't know what they were in for, actually. (LAUGHS) I knew that there would be certain days where working bees would be the solution. Right. A much better option than using a helicopter to get these in. So a good economic solution, free labour... Yep. And the great thing about doing it in the weekend is that Amelie's finally able to get her hands dirty. So, how are your muscles holding up, Amelie? (LAUGHS) Not bad. Actually I've been, uh... I'm stronger now cos I carry our 2-year-old around, so... Oh right. So is this the only way to do this, Amelie ` to get all these big, heavy blocks down to your site? Yep. (CHUCKLES) And also we're so busy, it's actually quite a good opportunity to socialise, see our friends. I guess the thing is ` this is just good training for you to carry the kids up and down and probably also to carry your shopping. CHUCKLES: Exactly. Karl: Five blocks to go! Four. Three. MAN: Two! Whoo! (CHEERING, APPLAUSE) (WHISTLING) Well, all I can say is ` the blockie will be very happy he didn't have to do that. Good effort, team. Wahey! Think you all deserve a good feed and a good drink. Fuelled by fish and chips and the Kiwi tradition of paying your mates in beer, this 20-strong chain gang will help balance out the environmental impact of the helicopter. We saved a fair bit of money doing it this way today. That's for sure. If we'd got the blockie to do it, I don't know how much he would have charged us. Isn't it wonderful to see this kind of conviviality? The build, very much in the spirit of barn raising ` and this city is full of it. But heartwarming as this is, friends and families have their own lives and can't be here every day. From here on, most of the hard work will be done by Tim, Max and Karl, and they have much bigger things to carry in than concrete blocks. By late May, the block wall of Karl and Amelie's Wadestown green home is up. And today, the house's timber frames are being delivered, and once again, the truck can only get them to the top of the neighbour's driveway. The neighbours have been great. The neighbour doesn't have to go out today either, so... Well, he can't now. (LAUGHS) It was lucky Dad thought about ordering these in time. That's why we have two project managers. These pre-nailed frames will save time and money, and because they're made to measure, there's no offcuts and no waste. And as a sustainable design practitioner, Karl has specified environmentally friendly timber. So I just took a photo of this imprint here which is emissions class, which basically means that they haven't added any urea-formaldehyde, which is bad stuff and is found in lots of building materials. So for our Homestar rating, we just need evidence that that's what we used, and nothing beats a photo. On a weekday, there's no mates or village here to help and no helicopter, so the real weight rests on Karl and Tim's shoulders. OK, swing round, Tim. And up, up, up. Tim's good. He's been awesome. He's a very strong boy. Whenever we need to move something or grunt something out of the way, we put Tim on to it, and it gets done in half the time. Yeah, this one's definitely heavier. You got the heavy end too. You're tough. It's been good to have someone here to work with Dad and keep things moving too, cos I can't be here all the time. There's a few more like this, eh. Well, I've got one more like this and then the four big ones. Oh great (!) It's a lot of work today ` they're effectively carrying down most of the house. But with the pre-fabricated frames onsite, the walls go up in an instant. The glue here is for insulation. Karl's energy plan relies on a completely airtight house. I've been very good at doing that, but it just means that every little crack is sealed. After all the complicated groundwork, this must feel like a real win. Very happy. Yep. Yeah. (LAUGHS) Pretty chuffed, really. It's great seeing Karl and Max getting on so well. And if they can keep this pace up, the house will take shape in no time. I can't wait to see it arguing for space among the trees. (JOVIAL CLASSICAL MUSIC) Having felt a bit left out of the build, Amelie has decided it's time to get on the tools. She's involved in a night school class to hone her woodworking skills. I've been desperate to get my hands stuck` to get stuck in. A swing is a great first project. It's not permanent and baby Claudie will love it, however it comes out. It's also good to take a bit of time from the week to do something that's for me, just for me, but it's also helping the house as well ` that sense of satisfaction of doing my bit. Amelie's also taking on more visible parts of the fit out ` a daybed and floating shelves for their living area. Karl will be looking at these every day, so there's more pressure to get it right. Well, I was hoping to use that. MAN: Yep ` to drill the holes. Yep. Yep. We're a bit tight on funds, and we got quotes for things, and we decided that we'd do it ourselves. But that's what really motivates me, is when it ticks multiple boxes ` it's fun, it's useful and it saves money. (LAUGHS) I knew that Karl had skills that I didn't have, but I'm trying to learn new skills so that I can take on more of the build and have fun with it as well, cos I think I realise that I do actually really enjoy making stuff. Karl wants to do it himself, plus with me and Max, so... That's the team, really ` Max and Tim and Karl and me. I admire Karl and Amelie for wanting to do it all themselves. But with day jobs and a small baby, I don't know where they get their energy from. (BIRDS CHIRP) While famous for its wind, Wellington actually gets more sun than Auckland. And on a magic winter's morning like this, you can see why Karl is banking on the house drawing enough heat to keep itself warm. What we have learnt about winter is that we get amazing winter sun, which we knew was there, but it's nice to be able to see it once the building actually comes together. I look at this and see how far they've come, but Karl, who's juggling the build and his day job, will just be seeing how much there is to do. I have been basically working six and a half days a week. I work a few hours on a Sunday, generally, and try and see Amelie and my daughter, Claudie, on Sundays. The long days and hard work are paying off, with the block wall back-filled and a lot of the retaining done. But August isn't traditionally a dry month in Wellington. I think once the roof's on, I'll be much more relaxed. Karl may be feeling the pressure, but his old-school father won't let him cut any corners. Well, why is it looking so ugly? What's ugly, mate? No, it's bowed. So, we've just put into place the fly rafter on the eastern end. We'll be straightening that. It's a little bit bowed at the moment, so we'll be straightening that. Do it this way so you can read it properly. Right up. 80 there. It must be bowed from the end out. 80 there. It's a bit more than 80` Yeah. Put it in, please. It's not much so far. Cramp it in with the cramp. It looks dreadful. It's bugger all. We'll just fix` No, get it now. You'll just cramp it there. Hold it there. That's looking much better already. Problems like this can make for long days for a small team, but Karl's real problem will be other people, and his biggest stress as the structure nears completion is making sure the roofers, plumbers and glaziers get their part done. Because Dad's time is so precious, the biggest stress-maker is when things don't get planned, and Dad can get grumpy, cos it holds him up. (JOVIAL ORCHESTRAL MUSIC) After two months' hard work, it's almost time for the roofers to come in. Wow. It's a house. A new skin of eco-friendly plywood is both structural and an extra layer in Karl's war on cold and damp. It looks like there's been serious progress, so I've come to find out how the small team are getting on. Gidday, guys. Gidday, Chris. Nice to see you. Nice to see you. And tell me ` how's the father-son thing going? Have you learnt a few things or...? No, it's been great. We've just worked away, really. Yeah. We shouted at each other a bit yesterday at lunchtime, didn't we, Karl? But, you know, got over that. We don't hold on to our grudges for very long any more. What do you mean 'any more'? Well, like, when I was 16, I'd get grumpy and stay grumpy, but now I just... (LAUGHS) It's OK. What about you, Max? Are you enjoying it? I have enjoyed it. But it's sort of wearing thin, you know, cos we're missing home. But, no, it's fine. We're gonna go home for quite some time this time. We'll go away in two weeks. We'll have the roof done. I mean, Karl can do the cladding. I don't need to be here. And how are you going budget-wise, generally? Mm... we're a bit over. What's a bit? (LAUGHS) A bit. Come on. Out with it. I can't` I can't, you know` I'm not sure yet. You're hiding it from me. Yeah. Well, I mean, a few things ran over, like waterproofing the back blockwork wall. I hadn't really thought` that wasn't really in the budget. It was missed?! It was missed. Wouldn't that be, like...? Oh, you know, it's a few grand, but it's... It hadn't been included, so that was a little bump. With so much on his mind, I'm not surprised Karl has dropped the ball on a few things, and it's only gonna get busier from here. They still need to get the house closed in, and that means cladding, lining, doors, windows, and, most importantly, the membrane roof. July was` I think it had 180% of its normal rain. August was pretty wet as well. And we're hopefully about a week away from getting the membrane put down. We're really just waiting for a fine, windless day. I'm concerned about Karl's whole zero-energy heating plan. He's totally relying on solar energy to keep his family warm, yet they can't even get enough sun here to get the roof on. (JAUNTY PIANO MUSIC) It's spring, and Karl and Amelie's Wellington home has come a long way. After a terribly cold and wet winter, the membrane roof is finally going down. While it looks like laying lino, installing the membrane is far more critical. With just two sheets covering the whole roof, they have to be perfectly lined up. If you're 5mm out down that end, by the time you get up to this end, you'll be 55mm out. So it's gotta be aligned correctly right from the start. And there's no second chance. Once it's stuck down, it stays stuck down. That's all there is to it. Certified safe for drinking from, this roof gets Karl additional home star points for harvesting rainwater. End of the day, and we're finished, so we're quite pleased. That's a very good day's work. A good roof. And we're going home now. With the house roofed and clad, it's starting to feel like it belongs here, so Karl can finally relax. Apart from doing the spouting and the little edges around the side, the roof's done. So it's a pretty big step. It's a pretty big moment. (LIGHT, LIVELY MUSIC) From the outside, it looks great ` almost finished. But there's still something missing. Had a few little issues, but, you know, that's normal for building a house. You're starting to sound like a real builder, Karl. 'A few little issues.' (LAUGHS) Like, what does that mean? The windows. (CHUCKLES) Maybe I should be asking somebody... (ALL LAUGH) Well, then... ...who's gonna reveal all. Come on, Amelie. Oh, we've just had a hold-up with the windows. It's kind of set us back a little bit. Mm. Why is it that it's so consistent that it happens pretty well all the time? Yeah, you tell us. Why's it always the windows? (LAUGHS) And they're, like, one of the biggest costs in the whole build. Yeah. Didn't you have a date that you were gonna move in? (LAUGHS) If we get the glazing before the end of the year, then I think we could possibly be done by, sort of, yeah, March, April. But if we don't, then it might be... Yeah, might be a bit later ` might be May. May? Originally, they'd hoped to be moving in by Christmas. But with no rush to move out of Amelie's parents' house, there's time to get things right. Karl reckons he's building a house that heats itself and that comes down to the relationship between the sun and the all-important concrete slab. They want more sun in winter and less in summer. So everything from window height to the width of the eaves and the deck comes into play. Karl's whole plan rests on getting those calculations spot-on. At lunchtime in December, the sun basically comes straight down and hits the edge of the deck and doesn't hit the slab, and so that's when we don't want any heat inside the house, because it'll be at a good temperature and it should just stay at 18 degrees. And then in winter when we want the heat, or the energy, the sun is a lot lower in the sky and it's coming in at that sort of angle and is, you know, going right to the back of the block wall and then that means our slab is receiving all of that energy and soaking it up to be released back into the space at night-time when temperatures drop. I guess the other thing that's wonderful about this battery is you never have to replace it. No. No, we don't. And it won't explode. (LAUGHS) This is about efficiency. It's about how healthy and warm your house is. And not just the impact of the build, but also the long-term ongoing impact on the environment, on your family and on your wallet. We should be thinking about these things with every single house we build. After delays over Christmas, the windows are finally in. And the walls and ceiling are packed with insulation, made in New Zealand from recycled plastic bottles, of course. The next step in the passive heating plan is lining the house with an airtight vapour barrier. Because this is something Karl recommends as a sustainable building consultant, he's pulled some workmates together and roped me in too. This might look like we're stapling a bunch of paper to the wall, but this is a high-tech material that creates an airtight layer over the insulation to keep heat in winter and protect against mould and damp. What do you reckon? Yeah, it's pretty good, actually. Yeah. It's sealed. Almost like a bought one. (LAUGHS) Airtight and moisture tight, Karl's theory is the house will keep itself warm, saving energy and money. But getting it right is more important than doing it fast. I think the main thing is, I wanna do it properly. And three more months at the end, or four more months are the end, is not gonna make, you know, any difference if I'm gonna sit there and think, 'Man, I wish I'd done that little bit.' You know, spent another half an hour on that bit and made it just that much better, or, you know... And I'm pedantic, so... Every working bee needs a barbeque. But Karl won't know if the wrapping has been a success until the house is nearly finished. If the airtight layer has too many leaks, the self-heating slab loses its sizzle. Four months later, it's a bitterly cold winter's day. The house is lined and plastered, ready for the moment of truth after all the work Karl's put in to his airtight layer. The blower door test ` pressurises the house and tests how airtight and how much air we're gonna lose. Right now we've just installed a false door, and it's got a nice big hole in it to put a ginormous fan in. For the ambitious energy plan to work, the house must be almost airtight to keep itself warm. So the blower door test sets up a vacuum to look for holes. If the house is airtight, you're not losing any heat through draughts or anything like that, and you can basically` yeah, you can control it. Let's go find some holes. Any hole in the airtight layer means Karl's house is sucking in cold air. The smoke puffer gives him a last chance to identify and fix the leaks. Power plugs are a big one. And Wellington, where we are, it's really common. You can feel air coming out of your plug sockets. It's pretty horrible, (LAUGHS) to tell the truth. We're going for below one air change per hour. And your average code-built house gets to about five to seven and could quite easily be a lot higher than that. (FAN WHIRRS) Yep, it's taking samples. All right. So turn it off. Yep, turn it off. And... This is the moment of truth. It really is. So at 50 pascals, you're at 0.8. Well done. Cool. Yippee. Nice one. Yeah, no, I'm very happy. That's great. You're a very humble man, I must say. Getting below one is absolutely phenomenal. The result is a huge win for Karl and reinforces his decision not to have a wood burner. We're just gonna have two small heaters ` about an 800W downstairs and an 800W upstairs. That's the goal, hopefully. But we can always put the fireplace in if we need to ` in the future, but we probably won't. As the house nears completion, Amelie's been spending more time on site with her new woodworking skills. Today, she and Karl are assembling a day bed for the reading nook. Basically, this is a design I came up with. I've never designed any piece of physical thing or furniture in my life, so it's a bit of a test to see whether it's actually gonna hold. Ever since we've been doing a lot of the internal work, I've been a lot more involved. With money running out, family have stepped in. Amelie's parents have been painting the interior, and today her mum has brought Claudie in to see Mum and Dad while she gets a quick coat on the stairway. It was actually my mother's idea to do it, cos she loves painting. So my 71-year-old mother and my 75-year-old father basically painted the whole house. Karl's grateful for the help, but it seems like the energy he's used building this energy-efficient house has left him exhausted. I mean, for me, it's just last month. It's that final push. And I'm a little bit... I could possibly be classed as a bit over it, at this point, so. I've enjoyed having a break during while the rest of the whanau's been painting. It's been really good. Had a few days off, so that's been nice. We just want to get in. I'm just over being` having this project looming over my head. I just want to get on with my life. Like... Feel I can go out to gigs and eat at restaurants. (LAUGHS) You poor thing (!) To see a young couple crafting their first home side by side is everything I love about building. But in a house designed to keep itself warm, the woolly hats are a bit of a worry. If they're still this rugged up when they move in, all the effort could have been in vain. (INTRIGUING MUSIC) It's been three months since I last visited Karl and Amelie's house, designed to draw all its heat from the sun, even in the coldest months of the year. Here we are in the middle of winter. Classic windy Wellington day. It's gonna be interesting to see if Karl's house actually works. (LIGHT ORCHESTRAL MUSIC) I really hope they have pulled it off, because this project has been ambitious right from the start ` an excessively steep site with over 100 steps as your only access. Wow. Looking very sharp. Hi, Chris. Hey. Welcome. Lovely to see you. You too. Kia ora, Chris. Wow, you guys have been busy. What a refreshingly simple design. I love the way they've turned economic materials like scaffold poles into a bold modernist screen. It's looking so beautiful. Can't wait to have a look inside. Yeah, we're really happy with it. Come on in. (SLOW PIANO MUSIC) Tada! This is it. Wow. Oh, you feel it straight away. It's fabulous. It's really working. Nice and warm. What I'm feeling is the lovely ambient temperature created by the sun soaking into the concrete that acts like a battery heating the whole house. It's blowing me away, because normally a battery like this takes a good season to work before it builds up that warm. Yeah, it's a good feeling. You can really feel it as you come in. You can feel that all the surfaces are nice and warm. But what's really clever about this design is the way the house responds to the sun at different times of the year. Because the sun is lower in the sky in winter, the tall windows allow a maximum amount of sunlight on to the slab. Whereas in summer, it's the opposite. Because the sun is higher in the sky, it actually won't hit the concrete slab. So the house won't overheat. Fabulous. So we'll be toasty and warm in winter and nice and cool in summer. (CURIOUS MUSIC) The overwhelming sense I'm getting here is one of complete harmony, where the simplicity of the wood and concrete aesthetic is driven purely by functionality, and that's why I call this a true grand design. I love the fact that it's just this wonderful big singular space, but then it's divided into this series of different rooms, almost, by the buttresses. The concrete buttresses create clever micro-spaces. Here, Amelie's made an office nook, a daybed and a little desk for 3-year-old Claudie. It's the first thing Claudie ran to when she came into the house, and she had her breakfast there and she had her toys there. It's been an excellent benefit of the design that I sort of mocked up halfway through the build. It looks absolutely gorgeous. I think it's really cute. Gosh, take me up to the stairs. (WARM MUSIC) This is Claudie's room. Oh, how cute. I love the little desk in the corner. Yeah, she really loves the space. We've continued the aesthetic of the groove panelling from downstairs up into each of the bedrooms to break it up a little bit. At the end of the corridor is Karl and Amelie's bedroom and en suite bathroom. We got first dibs on the sea view before Claudie had a chance to claim it. Really lovely having these big, large windows to sleep next to, and you can see the stars and the moon. Very nice. The metal screens and timber-clad decks create an external corridor looking down to the sea and across the valley. What a lovely spot. Decks that, no doubt, cop a fair amount of Wellington's unpredictable weather. Oh, now we're getting a decent gust. Here we go. That's more like it. There we go. Good old windy Welly. (LAUGHS) (BIRD SINGS) You guys have utterly blown me away, From the beginning, you two both felt very committed to rolling your sleeves up. Have you looked at numbers at all in terms of the sheer amount of hours that you two have done? Yeah, I think 2500 hours, probably. That's a few. (CHUCKLES) Yeah. That's a few. And Dad was here for 20 weeks; I was here for all of those 20 weeks. So, you guys wanted a house that could heat itself. How'd you go? Well, I think we managed to get there. If the sun comes out all day, the house is warm for three days. Boy, that must feel good. It does, yeah. So, what are the things that you absolutely love? Uh, I love all the natural light and that sense of peacefulness and serenity. I've always wanted to build my own house, and it's a pretty` yeah, it's a great feeling to actually have achieved that. How did it pan out in terms of the cost? We spent a little bit more than our budget. A little? Yeah. What does that mean? (LAUGHS) I think we came in about 480. So what's that? Is that about 80,000 over what you originally thought? Yeah, well, I think we said 400. But then maybe qualified that and said it's probably gonna be more like 450. What have you learnt from each other? (BOTH CHUCKLE QUIETLY) I've learnt that Amelie can spend a lot of time looking at lights. (LAUGHS) Yeah, and Karl's quite obsessed about insulation. (LAUGHS) And thermal performance. I think it's definitely, like, challenged us, in terms of, we've both been under high stress... Mm. ...and we ended up bickering quite a lot. (LAUGHS) But then, yeah, sort of bickering and the be like, 'Oh, sorry.' But knowing in the scheme of things that it was just` you know, it was a passing phase. Yeah. And that we were doing something really cool together. So does that mean you would do it all again? (CHUCKLES) Uh, no. (LAUGHS) We wouldn't do this project again. The goal now is to try and get the rest of New Zealand to build in a similar fashion. So much of the value of this house is in what you can't see ` the insulation, airtightness and the way it shapes the sun to heat its concrete battery. The result means Amelie and Karl have a warm, comfortable home that cost little to run. But what I really love is its humble simplicity that feels as Wellington as the hills it's sitting on. (ALL CHEER) Captions were made with the support of NZ On Air. www.able.co.nz Copyright Able 2018