Build­ing on the foun­da­tion of the in­su­la­tion and heat­ing grants for New Zealand homes, we have much more to achieve in terms of en­ergy ef­fi­ciency.

Element - - Element Promotion - By Leigh Feather­stone LEIGH FEATHER­STONE

You may not be aim­ing to build (or ren­o­vate) to ul­ti­mate eco-house stan­dards, but un­der­stand­ing the causes of wasted en­ergy and thus wasted money makes sense at ev­ery level.

En­ergy used in house­holds mat­ters be­cause it ac­counts for about 12% of all NZ’s en­ergy de­mands. That’s about twice as much as all non-in­dus­trial com­mer­cial use. So where does it all go? Ac­cord­ing to EECA in the aver­age home en­ergy bill wa­ter and space heat­ing ac­count for about 30% each, elec­tron­ics 12%, re­frig­er­a­tion 11% light­ing 6%, and cook­ing and the rest 11%. To make big sav­ings it’s most im­por­tant to deal to space and wa­ter heat­ing. Smart de­sign­ers and ar­chi­tects un­der­stand this and de­sign ac­cord­ingly. So, what are the most im­por­tant things? First, it is about size, ac­tu­ally. We are sec­ond only to Aus­tralia in build­ing the largest homes in the world. Don’t mis­take a low $ per square me­tre build­ing cost as value for money. Ask your­self if you re­ally need a bath­room the All Blacks could get changed in, or if you need four bed­rooms, be­cause you’ll be pay­ing the bills for heat­ing them.

Sec­ond, in­su­late, in­su­late and then in­su­late some more. The build­ing code only spec­i­fies a ba­sic level. Go­ing be­yond this in ceil­ings, floors and walls does not cost much more as the labour in­put is about the same. 25% of heat is lost through win­dows, so dou­ble glaz­ing is a good idea if it’s a ther­mally bro­ken sys­tem, i.e. the ac­tual frames have an in­su­lat­ing layer in them. A key term to drop here is ‘ther­mal en­ve­lope per­for­mance’.

Thirdly, think about heat­ing. Fun­nily enough the best heat source is free and we call it the sun. If at all pos­si­ble your main liv­ing area should have a north or north-west as­pect. Good ther­mal mass de­sign soaks up the free heat and re­leases it as the day cools. You may also want an­other heat source. Heat pumps are gen­er­ally ef­fi­cient but be care­ful about the spec­i­fi­ca­tions and ac­tual per­for­mance in your re­gion. One that’s good for Whangarei may not be so hot in Ar­row­town. Also think about wood burn­ers and pel­let burn­ers if lo­cal reg­u­la­tions per­mit.

Now. Let’s risk get­ting into hot wa­ter be­cause at 30% of a typ­i­cal bill wa­ter heat­ing is a ma­jor un­less you are able to in­stall pho­to­voltaic (PV) cells on the roof to pro­vide the elec­tric­ity. Rel­a­tive costs and tech­nol­ogy are chang­ing all the time, so look around for op­tions, par­tic­u­larly hot wa­ter heat pumps. In­stant heaters re­main a good bet, es­pe­cially for smaller house­holds.

New homes at Hob­sonville Point in Auck­land em­body many of th­ese de­sign prin­ci­ples. The homes are a bit smaller than the Kiwi norm but that means less space to heat. They are very well in­su­lated and rely mostly on heat pumps for heat­ing. They have so­lar hot wa­ter or pho­to­voltaic so­lar panels. Pre­lim­i­nary data from a study by Vec­tor in­di­cates that home by home, street by street, the en­ergy ef­fi­cient homes at Hob­sonville have sig­nif­i­cantly lower than aver­age en­ergy bills.

Most New Zealand new homes typ­i­cally reach only Homes­tar three or four. Hob­sonville Point homes are typ­i­cally 6 Homes­tar and some builders are now pro­duc­ing 7 and 8 Homes­tar-rated houses. Peo­ple of­ten per­ceive sus­tain­able en­ergy ef­fi­cient homes as ex­pen­sive, but they are be­com­ing main­stream and af­ford­able.

Re­cent stud­ies by Jasmax and eCubed showed a typ­i­cal three-bed­room house in the Auck­land re­gion built to Homes­tar 6 would cost only an ad­di­tional 2.16% to build and would be off­set by a re­duc­tion in en­ergy and wa­ter costs in about five years. Or if the house was about four square me­tres smaller there would be no in­crease in con­struc­tion price.

Hav­ing sorted out the big stuff with heat­ing and hot wa­ter, what about the re­main­ing 40% of en­ergy use? Well, here it can be fun be­cause it is about shop­ping and us­ing your smarts. Ap­pli­ances that are En­ergy Star-rated by EECA are your friend. Down­lights are not your friend, be­cause they put holes in your in­su­la­tion. Avoid them or spec­ify those that can be cov­ered by in­su­la­tion. You’ll want CFL or LED light bulbs be­cause they use 80% less en­ergy and can last for 20+ years. Smart me­ters are here now. This tech­nol­ogy is a plat­form for all kinds of en­ergy ef­fi­ciency good­ies be­cause sen­si­tive mea­sure­ment of use is the key to man­age­ment of use. For ex­am­ple, Merid­ian has no­ticed that 25,000 homes in Christchurch seem to use more power at off-peak times. So just by switch­ing to an off-peak pric­ing plan th­ese home­own­ers will make sub­stan­tial sav­ings. This is good for New Zealand too - the more off-peak use we en­cour­age the less peak time gen­er­a­tion ca­pac­ity we need to pro­vide. Oh, and put a timer on your towel rails. Ac­cord­ing to EECA that’ll save the coun­try $70 mil­lion dollars a year.

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