Lifespan of SIPs

[TomM]

So, there’s lots out there about pros and cons of SIPs but I’m conscious they’ve only really been around for about 60-70 years.  (The biggest risk seems to be water ingress - but that would be the same for timber frame, right…?)

 

So, if well built and well maintained, how long will a SIPs house last?  The only figure I’ve seen is 60 years.  But that is conveniently around the same length of time as their existence!!

 

Any informed views out there?  Many thanks.

[Kelvin]

They’ve been around longer that 60 years. First experiments of SIPs build go back as far as the 1930s and the first real commercial use goes back to the early 1950s. There’s no reason not to expect them to last as long as any other construction method if well built and well maintained. 

[JohnMo]

I toyed with the idea for our build.  Looked and came to conclusion if you want them to last you need to pay attention to a possible cold bridge between the SIP and foundations. A lot of the plans I saw had a good cold bridge at that location, which could lead to moisture being developed due to condensation, then rot etc. The same would be true for timber frames in general.

 

Other than that as long as the wood is kept dry it should last.

[PeterW]

Cold bridging at the sole plate and detailing there for condensation is the biggest problem. Some use a sheath of PIR over that point but not seen a good solution yet unless anyone else has.

 

 

[Kelvin]

Sure but that’s something that will happen relatively quickly. If it lasts 10 years (length of warranty) it should last decades. It would also affect timber framed buildings and there are thousands of those being built and most new houses in Scotland are timber frame. 
 

It is possible to add EPS on the outside of the SIP panel above and below the sole plate and affix the sole plate to a foamglass type product. 

Edited December 30, 2022 by Kelvin

[TomM]

Thanks.  I’d read about the biggest problem area being the sole plate junction.  And seen some references to Marmox blocks (?) as a possible solution. But ideas outlined above, and reassurance that, well built and well maintained, SIPs should last just as well as other methods of construction gives me confidence.

[ProDave]

What is fundamentally different to a timber frame with insulation in the frame, and a SIP panel, that makes SIP panels prone to sole plate condensation and timber frame not so?

[Kelvin]

I don’t see how they are different as you still end up with a wooden sole plate at the top of a block on the cold side assuming a traditional foundation design. 

[SuperJohnG]

I have a sips house, and an insulated foundation from Kore. No brick or block here just a ventilated cavity. 

 

You have a sole plate (as do all timber frame houses) then a locator plate, which is just like a sole plate but smaller and allows the sip panel to sit over it and onto the sole plate. 

 

You add 200mm high of 25mm pir around the junction between insulated foundation (as per the drgs) and soleplate and Bob's your uncle. 

 

This worry about interstitial condensation is overthought. All houses that have a wooden sole plate this applies to.

 

Even if water was to get in and sit at the soleplate or have condensation - it's treated timber.