In­su­la­tion vi­tal for warm homes

Matamata Chronicle - - Winter Warmth -

Awell-de­signed new home or ren­o­va­tion has an en­ve­lope of in­su­lat­ing ma­te­ri­als in its ceil­ings, floor and walls that keep it warm dur­ing win­ter and cool dur­ing sum­mer.

A home that keeps in the heat has: plenty of in­su­la­tion ther­mal mass good dou­ble-glaz­ing with in­su­lated frames

a good level of air­tight­ness.

Good in­su­la­tion is the key to a warm and com­fort­able house that doesn’t cost a for­tune to heat. And the best time to do it is when you are build­ing so you can ac­cess all ar­eas as you go.

For a re­ally well-in­su­lated new home: Make room for your in­su­la­tion. For tim­ber- or steel-framed houses, use 150 mil­lime­tre or even 200mm fram­ing in ex­ter­nal walls and re­duce the num­ber of fram­ing mem­bers to what is struc­turally nec­es­sary – this makes more room for in­su­la­tion.

Ex­ceed the min­i­mum Build­ing Code in­su­la­tion re­quire­ments.

For bet­ter warmth and com­fort, it is worth putting in more than the min­i­mum in­su­la­tion lev­els, es­pe­cially if you are in a colder part of the coun­try.

In­su­late cav­i­ties be­fore they be­come in­ac­ces­si­ble. Some cav­i­ties be­come in­ac­ces­si­ble by the time nor­mal in­su­la­tion in­stal­la­tion hap­pens, so it is im­por­tant to in­su­late them be­fore­hand.

Ar­eas such as ex­ter­nal and in­ter­nal wall junc­tions, win­dow lin­tels and block­ing of dou­ble studs are usu­ally only ac­ces­si­ble from the out­side and should be in­su­lated just be­fore the wall un­der­lay is in­stalled.

If you have steel frames, a layer of in­su­la­tion is needed be­tween them and outer cladding to pre­vent ther­mal bridging. The NASH House In­su­la­tion Guide pro­vides guid­ance.

Make sure the hol­low steel pro­files get com­pletely filled with in­su­la­tion. This is a com­mon in­su­la­tion in­stal­la­tion fault in steel framed con­struc­tion.

If your house has an at­tached garage, in­su­late the in­ter­nal walls and ceil­ing be­tween the garage and the rest of the house.

If you have a skil­lion roof, choose 240mm or 290mm rafters that pro­vide enough room for good, high R-value in­su­la­tion while still al­low­ing for a 25mm gap be­tween the in­su­la­tion and the flex­i­ble roof un­der­lay. If you have a con­crete-slab floor, make sure it is well in­su­lated.

In­su­lat­ing both un­der­neath the floor, around the foot­ings and around the perime­ter re­duces heat loss.

Avoid re­cessed down­lights. They re­quire holes to be cut in your in­su­la­tion for fire safety rea­sons, which cre­ates heat loss. They can also cause draughts. Min­imise plumb­ing and electrics in ex­ter­nal wall cav­i­ties – they can make it im­pos­si­ble to in­stall in­su­la­tion prop­erly in af­fected cav­i­ties, and can af­fect the build­ing’s air­tight­ness. Try to lo­cate such ser­vices in in­ter­nal walls in­stead. Plan your con­struc­tion work­flow well so that once the in­su­la­tion is in­stalled it won’t get dis­turbed by other trades.

Get it in­stalled prop­erly. In­su­la­tion doesn’t per­form well un­less it is in­stalled prop­erly.

Have your in­su­la­tion in­stalled ac­cord­ing to the New Zealand Stan­dard 4246:2006.

Dou­ble glaz­ing is now stan­dard in new homes as it is the eas­i­est way to meet the cur­rent Build­ing Code in­su­la­tion re­quire­ments. It still lets in as much sun­light as sin­gle-glazed win­dows or sky­lights, but dou­ble glaz­ing is much bet­ter at retaining heat.

Some dou­ble-glaz­ing is bet­ter than oth­ers. For best per­for­mance, look for the fol­low­ing things.

Frames that are ther­mally bro­ken, or made from an in­su­lat­ing ma­te­rial such as PVC or wood.

These will per­form bet­ter ther­mally than win­dows with stan­dard alu­minium frames. It can re­duce win­dow heat loss by about 20 per cent (ther­mally bro­ken alu­minium frames) to 40 per cent (PVC or wooden frames), com­pared to dou­ble-glaz­ing in stan­dard alu­minium frames.

Low-emis­siv­ity (low-e) glass. This al­lows light and heat in, but re­flects es­cap­ing heat back to the in­side.

Low-e glass cuts win­dow heat loss by about 20 per cent to 30 per cent, com­pared to dou­ble-glaz­ing with­out low-e Mul­ti­ple lay­ers of good seals to keep draughts, mois­ture and noise out.

The joint be­tween the glaz­ing unit and the frame also needs to be well-sealed. Spac­ers made of plas­tic or stain­less steel to sep­a­rate the glass panes (in­stead of alu­minium) to re­duce heat loss and con­den­sa­tion at the glass edge.

An in­ert gas fill­ing (such as ar­gon) be­tween the glass lay­ers. This acts as a bet­ter in­su­la­tor than air, re­duc­ing win­dow heat loss by about three per cent to nine per cent, com­pared to dou­bleglaz­ing with air fill­ing.

Close-fit­ting ther­mal cur­tains will re­duce heat loss through dou­ble-glazed win­dows even fur­ther.

When choos­ing sky­lights it is crit­i­cal to pick ones with good ther­mal per­for­mance char­ac­ter­is­tics to avoid high heat losses on cold win­ter nights and over­heat­ing in sum­mer. Apart from the fea­tures listed above, it is highly rec­om­mended to se­lect one with a low so­lar heat gain co­ef­fi­cient and to in­stall ef­fec­tive shad­ing de­vices to block out the sun on hot sum­mer days and to im­prove in­su­la­tion on cold win­ter nights.

Sky­lights that open can be ef­fec­tive for sum­mer cool­ing through ven­ti­la­tion. If your sky­light is in­stalled through a roof space make sure the light­shaft is well in­su­lated.

Even well-in­su­lated houses can be hard to heat if draughts con­stantly re­place hot air with cold air.

Good build­ing air­tight­ness, cou­pled with con­trol­lable ven­ti­la­tion (like open­able win­dows, vents or me­chan­i­cal ven­ti­la­tion sys­tems), lets you man­age air re­place­ment and avoid un­nec­es­sary heat loss. For good air­tight­ness: Plan for air­tight­ness dur­ing the de­sign stage. This means all de­sign de­tails can al­low for proper, con­tin­u­ous seal­ing with­out gaps.

De­sign sim­ply. Fewer con­struc­tion joints means less po­ten­tial for air leak­age. Min­imise ex­ter­nal wall pen­e­tra­tions.

Holes for elec­tri­cal and plumb­ing ser­vices can re­duce air­tight­ness – aim to have them through in­ter­nal walls in­stead.

Make sure it’s well sealed. That means the join­ery and the wall, floor and ceil­ing con­struc­tion should all be prop­erly sealed.

This can be done with air­tight­ness mem­branes, which have re­cently be­come avail­able in New Zealand at some hard­ware stores.

The store or the man­u­fac­turer should be able to ad­vise you on the best so­lu­tion for your cir­cum­stances.

Use air­locks at ex­ter­nal en­trances to your home, which are a buf­fer be­tween in­side and out­side your home.

En­try ways, laun­dries and at­tached garages can all func­tion as air­locks.

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