Smart Se­ries: the 10/10 house

De­signer War­ren Clarke is so pas­sion­ate about smart homes, he built one of the smartest in NZ.

NZ Lifestyle Block - - Contents - Words Nadene Hall Im­ages Nook

Why War­ren Clarke’s home is one of the smartest in NZ

If there's one thing War­ren Clarke would change about his small, smart house, it's the size. At 140m², it's al­ready 42m² less than the av­er­age NZ home, and he'd make it smaller. “Some­body asked me, if I could do it again, what would I change? I reckon I could take 10-15m² out of it and it would still be amaz­ing.”

Over­sized, in­ef­fi­cient houses are one of War­ren's pet peeves. He spent years work­ing for a build­ing com­pany, de­sign­ing big­ger and big­ger homes that met the min­i­mum stan­dards re­quired un­der the Build­ing Code. Un­der the code, an in­ef­fi­cient, poor­lyin­su­lated, ex­pen­sive-to-heat home still meets the min­i­mum stan­dards.

It an­noyed War­ren so much, he went to work for de­sign com­pany, Nook.

“Bud­get and cost were al­ways paramount. I learned ways of de­sign­ing houses so that they cap­tured the sun bet­ter, were warmer. I tried as much as I could to get more in­su­la­tion into them and make them more en­ergy ef­fi­cient, but there was al­ways a push­back from the client: what's it go­ing to cost, what's my pay­back for that sort of thing?”

War­ren's ar­gu­ment is that an ef­fi­cient home is go­ing to save you money for decades. He's ob­served power prices have gone up 100 per­cent ev­ery decade since the 1970s.

“If your house to­day costs you $650 a month to heat, in 20 years' time it's go­ing to be $2500. If you in­vested that $2500 in the build in the first in­stance, you wouldn't be spend­ing that. ▶ Con­tin­ues on page 30.

“I could have built a 200m² home and it would have cost me $4000-5000 to heat it ( yearly). Instead, I have a 140m² home and I can heat it for $1500 a year.”

Build­ing smaller means money can be in­vested in prod­ucts that will keep the house warm and en­ergy-ef­fi­cient for a life­time.

A small house has other ben­e­fits. War­ren’s first de­sign in­cluded a garage.

“But we had to save some money and I thought, ‘right, we’ll have a stor­age box with a car­port’. It’s the best thing that ever hap­pened – you don’t have so much junk! You look at things and go ‘how im­por­tant is this to me?’ I went through 20 years of garage junk, and said, ‘nope, I haven’t used that, nope I haven’t used that. It was cathar­tic.”

The Brief

War­ren’s home was in­spired by his clients. They would of­ten ask what was the ‘pay­back’ on size and cost. War­ren de­cided to find out.

“I thought, I’m go­ing to build a house, we’re go­ing to live in it for 3-5 years and we’re go­ing to find out once and for all what’s worth it and what’s not.”

A good smart home will be much smaller than the NZ av­er­age of 182m² (ris­ing to 217m² in Auck­land). Money saved on build­ing ex­tra square me­tres can be in­vested in prod­ucts and tech­nol­ogy that will make it a more ef­fi­cient, warmer, and health­ier home for 50+ years.

War­ren’s ini­tial idea was to de­sign a house that would be a 7-8 on the Homes­tar rat­ing scale (see page 35). But his builder was more com­pet­i­tive.

“He asked me, what would take it to a 10? I told him: acous­tics, so­lar pan­els, grey­wa­ter re­cy­cling. He said ‘let’s give it go’, and we did it.”

The de­sign is pas­sive house, and War­ren also fol­lowed the ba­sic prin­ci­ples of smart, small homes (see page 30).

A 10 Homes­tar house is built to world-lead­ing stan­dards, with strong sus­tain­able cre­den­tials. War­ren’s home is only the third in NZ to pass the strin­gent qual­ity assurance tests, over­seen by the in­de­pen­dent Green Build­ing Coun­cil of NZ.

"It's the best thing that ever hap­pened – you don't have so much junk!"

The De­sign

Many of the fea­tures of this house are things you can't see, but each one played an im­por­tant part in gain­ing that magic 10 rat­ing.

The waf­fle slab floor (also known as a ‘raft' slab) sits on a spe­cial layer of in­su­la­tion. An­other in­su­la­tion layer wraps around the edges (80% of heat loss is out the sides of a con­crete floor). It is also an im­por­tant part of the home's heat­ing sys­tem (see page 34).

A waf­fle slab sits above the ground so it's eas­ier and cheaper to in­stall than tra­di­tional foot­ings which must be dug out. Sty­ro­foam pods sit in the con­crete, re­duc­ing the amount of con­crete you need to use. This also makes the slab lighter, al­low­ing you to build on soft soils.

It's seis­mi­cally strong. That's im­por­tant when you're build­ing a house in the still earth­quake-rav­aged suburbs of Christchurch, says War­ren.

“In an earth­quake when the ground moves, (the foun­da­tion) just sits there and vi­brates – it floats like a raft. I came to Christchurch in 2011 af­ter the earthquakes, and I had been us­ing raft floors for 4-5 years be­fore that. But it was new tech­nol­ogy to Christchurch, they didn't know what I was talk­ing about. Now, it's vir­tu­ally stan­dard.”

The lam­i­nated ve­neer lum­ber fram­ing wood is 140mm wide, instead of the con­ven­tional 90mm. The ex­tra thick­ness helps to in­su­late the house; stan­dard 90mm tim­ber fram­ing acts as a ther­mal bridge, trans­fer­ring heat out of a house due to its nar­rower width.

A 50mm cav­ity runs around the in­side of the fram­ing, to house pipes and ca­bles, main­tain­ing the in­tegrity of the air­tight lay­ers.

“The fram­ing be­comes a rigid air bar­rier, and you don't want to pen­e­trate that, so all my wiring and plumb­ing goes into that ser­vice cav­ity. It means I can cut holes in the walls, put in elec­tri­cal plugs and put my taps out through it, and I'm not punc­tur­ing (the rigid air bar­rier).”

It's an added cost to put in a cav­ity like

"In an earth­quake when the ground moves, (the con­crete floor) just sits there and vi­brates – it floats like a raft."

War­ren Clarke

this, but a well-thought-out lay­out can save you money. For ex­am­ple, if bath­rooms and the kitchen sit along the same ex­ter­nal wall, you only need a cav­ity along that wall, not all the way around the house.

“It's that whole thing of look­ing and plan­ning at the de­sign stage," says War­ren. "You can plan sav­ings.”

To gain a 10 Homes­tar rat­ing, War­ren had to think about air qual­ity. A spe­cial ven­ti­la­tion sys­tem keeps the air fresh, while still re­tain­ing heat (see be­low).

He used H1.2 treated wood that pre­vents fun­gal and bug in­fes­ta­tion. It is low VOC (volatile or­ganic com­pounds), mean­ing it doesn't re­lease much (or any) toxic gas or vapour. It's cov­ered with build­ing wrap so any gases that are pro­duced can't get in­side the house.

“We also used an or­ganic, nat­u­ral paint fin­ish on the plas­ter walls, and no formalde­hyde.”

Two other fea­tures to help the house reach 10 Homes­tar are its rain­wa­ter stor­age tanks and a re­cy­cling grey­wa­ter sys­tem. The grey­wa­ter from the shower, bath and van­i­ties is re­cy­cled, then used (along with rain­wa­ter) in the toi­let cis­terns and laun­dry.

The Heat­ing Un­der­floor hy­dronic heat­ing sys­tem and air-sourced heat pump

This sys­tem moves hot wa­ter through pipes in the con­crete floor. An air-sourced heat pump warms a 360-litre hot wa­ter cylin­der. Hot wa­ter is taken from the bot­tom of the cylin­der and pumped through the floor.

Heat re­cov­ery air ven­ti­la­tion sys­tem

A heat re­cov­ery ven­ti­la­tion sys­tem re­freshes the air in the house, help­ing to con­trol hu­mid­ity and pre­vent mould.

“When you have a lack of air move­ments, you've got to me­chan­i­cally vent the house, or you get a build-up of con­den­sa­tion, a build-up of CO₂, and you'll have prob­lems with mould," says War­ren. "We ex­tract the warm, moist, dirty air; the in­com­ing, clean, cold air passes the out­go­ing air and the heat is ex­changed… it's 80% ef­fi­cient.

“The heat pump and our un­der­slab heat­ing give us a lot of gains. But also, be­ing near-pas­sive, we build up our ther­mal mass so our con­crete slab be­comes al­most a bat­tery, stor­ing heat.”

OM so­lar ven­ti­la­tion

OM comes from the Ja­panese words ‘omoshi­roi' (in­ter­est­ing) and ‘mot­tainai' (non­waste­ful). It's a se­ries of vents and fans that suck warm air in dur­ing the day and down ducts into the house to help warm it.

War­ren's sys­tem was de­signed by a friend and in­te­grated into the ven­ti­la­tion sys­tem.

The Re­sult

A year later, War­ren's house has passed the strin­gent test­ing by Homes­tar, scor­ing the high­est pos­si­ble rat­ing. His house is only the third in NZ to reach a 10.

“I still wan­der around my house and look at it and think ‘wow, it's amaz­ing', and I've been liv­ing in it for a year.”

He's now work­ing with clients who want smarter homes, and with builders who are keen to to try the new tech­niques and prod­ucts needed to con­struct them.

“Of­ten peo­ple come to us and they're al­ready of the smart house mind­set: they've of­ten re­searched it for 3-5 years, they've been to open homes. They know in their bones if they go to a vol­ume builder, they're not go­ing to get what they want.

“You tell them you can take the bud­get they've got and build a smaller house, but it'll be much more en­ergy ef­fi­cient, much nicer to live in.”

War­ren says those in warmer cli­mates could learn a lot about build­ing smarter.

“Auck­lan­ders don't think they need to worry about en­ergy ef­fi­cient hous­ing, but it's not only for places with cold win­ters. Smarter houses are warmer in win­ter and cooler in sum­mer. It ben­e­fits ev­ery­one, from Bluff to 90 Mile Beach.

"We've had days here where it's 30°C out­side, and we can main­tain 25°C in­side with­out cool­ing it."

Most peo­ple think short term, says War­ren. They build enor­mous, in­ef­fi­cient houses and put their bud­get into what he calls ‘bling'.

“We've spent too many years go­ing down a path where we build rub­bish hous­ing and go for gran­ite bench­tops and the most ex­pen­sive tiles. Then you find it costs $500 a month to heat.

“If you have a smaller, smarter home, it's eas­ier to heat, eas­ier to main­tain.

"The prob­lem is we don't treat our homes as a home, we treat them as a fi­nan­cial as­set, and that's just wrong.”

Top photo: War­ren used de­sign tech­niques to make the 140m home look big­ger, in­clud­ing a high, slop­ing ceil­ing to give it more vol­ume. The view when you walk in the front door takes in the en­tire main liv­ing area, and leads the eye out through the French doors, into the gar­den.

A good small house has flex­i­ble spa­ces. The me­dia room is also War­ren's of­fice, and can be used as a bed­room.

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