Should we pay out for Kingspan insulation boards being applied to theexterior of our house? We bumped into a friend the other day and shewas with a friend who is an architect. When he heard that we are aboutto have shiplap weatherboard cladding applied to the exterior of ourhouse he said it would be easy to have Kingspan insulation boards fittedbetween the batons which the weatherboard will be nailed to and thatthis insulation would make a BIG difference to the warmth of the houseinside.The outside of our house is incredibly ugly with badly applied concreterender, or "roughcast", splattered all over it. The weatherboardingwill hide all that AND also look very good once stained. But now we arewondering whether to ask the builders to fit Kingspan between the renderand the weatherboard.Previously we got a quote for tearing off all the plasterboard inside,pulling out the fibreglass wool between the studs, fitting Kingspan,applying new plasterboard in all the rooms, and skimming over. Thequote was a shock! Ridiculously expensive - not because of theinsulation but because of the plasterboarding and the plastering. Sothe whole idea had to be dropped.But slipping Kingspan over the outside surface before nailing on theweatherboarding would be easy and wouldn't push the price up too muchapparently. So the architect said and our builders agree. (They'reworking out a quote.)But the big question is: would it make a noticeable or worthwhiledifference to the temperature inside? What do you think? Has anybodydone this already?All feedback much appreciated.Eddy.

Damn good idea if your building is stone or brick and you are havingweatherboarding anyway. The more the better but detailing criticali.e. if draughts can bypass the insulation then it's worthless, on awindy day especially. Also there would be an eaves detail where thenew work sticks out. If not masonry then insulation outside or withinthe wall makes no difference in principle. Masonry would act as a'heat sink' and slowly warm up to average room temp, radiating heatback when the heating is off, or during the night after summer daytimeheat has been absorbed.cheersJacob

Apply Kingspan to the EXTERIOR of house?

Mar 14, 2008 28 Replies

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Andy Wade 18 years ago

No it doesn't actually. The 'thermal mass' - strictly thermal capacity, i.e. mass times specific heat - of the masonry isn't affected by adding insulation. OK, the insulation itself has some thermal mass, but that will usually be negligible in comparison to the mass of whatever's being insulated.

- it turns the masonry into a heat reservoir

What you're trying to say is that it increases the thermal /time constant/.

Time constant of a structure = (mass * specific heat) / (U-value * area)

(First-order system approximation.)

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normanwisdom 18 years ago

Yes but it's useful performance as a thermal mass has value if insulated on the outside , so there tit head

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Andy Hall 18 years ago

That rather depends on whether one *wants* thermal mass.

The other side of that coin is what happens if the weather changes and temperature changes?

If you have high thermal mass to contend with then it will take longer to address the effects of that.

Storage heaters and underfloor heating are examples of that. The former are worthless and the latter need careful operation.

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Grimly Curmudgeon 18 years ago

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Doctor Drivel" saying something like:

Bad day for reading comprehension, is it? He quotes that as being the type of thing that's said by the ignorant.

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Doctor Drivel 18 years ago

Matt, you must understand thermal mass and its benefits. Buy "The Whole House Book".

The heating system adjust to suit. Matt, you really don't know.

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Andy Hall 18 years ago

I didn't say don't do it. I said understand the implications.

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Doctor Drivel 18 years ago

Matt, you still don't know.

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Andy Wade 18 years ago

Actually in well-insulated buildings with long thermal time constants (achieved through the use of high thermal mass) they can work very well.

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Andy Hall 18 years ago

Not many of those though...

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