SIPS – extension pros & cons? longevity? price?

[Anonymous]

Unfortunately the search engine's not working at the mo on the AECB site, because I'm sure this question's been asked before…

I've known about SIPS for quite a while and somehow ignored them, but it's slowly dawned on me that maybe I'm missing a trick here. I'm trying to get my single skinned 1925 house up to a reasonable level of thermal efficiency. My plan for getting there involves insulating the floors, building a porch, installing MHRV, EWI the walls and doing an extension with south facing windows – in roughly that order.

It occured to me that if I did the porch in SIPS, I wouldn't have to worry about EWIing it to avoid thermal bridging – and the walls might be thinner to achieve the same u value, giving me more space. The same argument applies to the extension, especially as I'd like to have the upstairs roof open to..well, there wouldn't be rafters, I suppose, but I don't know the technical term. As I understand it, SIPS construction is more airtight too, which would fit with mhvr and just generally keeping the heating costs down.

However, having completely ignored sips previously, I don't know what the cons are. I saw a video on a sips manufacturer's site that rather put me off just because the sips looked so flimsy compared to bricks and mortar, but I don't know if that's just prejudice? I also wondered about marrying masonery with a different material? I also wondered about proven longevity? Someone also wondered how the issue of damp is addressed in these systems?

I'd really appreciate some advice & comments on this as I don't think it's wise to take the manufacturers word for it!

thanks,

Tania

[Anonymous]

Have you considered icf? Thermal Mass, low thermal bridging, low air permeability, won't support mold, high fire and element resistance, high sound attenuation, longevity, simplicity

[Anonymous]

I did actually. I'm still mulling it over, but I was of the impression that icf Walls would have to be substantially thicker to achieve a similar u value & I dont have much space..:-(

[Anonymous]

U values are just numbers and do not reflect the true value as to how a wall performs. We have built the first Net Zero/Zero Carbon school in the USA with a wall u-value of 0.24 and this is backed up with ACTUAL running data as the Americans have a nice saying “In God we trust, all others bring data”. I have documented homes in Ireland that have values of 0.24/walls, 0.28/floor, 0.16/roof with a total energy use of 35.78 kwh/m2/yr. The 0.24 wall with plasterboard inside and a render outside will have a width of approx 306mm and a 0.25 wall approx 255mm so yes, an icf does have that one disadvantage.

[Author]

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