See today's comments in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2847&page=2#Item_20 - SIPS are resolutely artificial, with all the health/performance implications of that.

I'll declare my interest before joining in here - we're about to build a SIPs based house and are sold on the technology. It meets our requirements very well and, unlike some 'green' technologies, to borrow a phrase "does what it says on the tin". There's no arm waving and guessing when it comes to establishing the ability of SIPs construction to deliver a well insulated, energy efficient home. That said, they don't seem to be terribly popular around here.

SIPs have been around for over half a century, so there seems to be quite an established body of evidence as to their long term performance. As I understand it, they can be treated as a 'heavy' timber frame, so foundations need be no different from that construction technique. Our SIPs supplier was able to give us line loads and from that a structural engineer could calculate the appropriate foundation details.

As it's a different construction technique, you have to plan appropriately. If you're in the camp that believes in high thermal mass, you'll need to provide that mass in addition to your walling system - that would be the same if you were using traditional timber frame. Air tightness is high, so for whole buildings a ventilation system is a must. For your extension, you might need to take advice. SIPs can only deliver 'lego like' construction if your foundations are very accurate - alterations on site to cope with an innaccurate base are time consuming and fiddly. As everything is prepared off site, you have to anticipate every detail of the construction. That's very different from most other techniques where you have the flexiblility to adjust details ("bodge" it!) as you build.

If you wish to avoid petrochemicals and CO2 production in building your extension, you'll have to weigh up the relative merits of the many different construction techniques. If you want truly green (and almost lego-like!) construction, you could consider straw bales - though if you have space constraints (as we have), the wall thickness can be an issue. Apart from straw bales, our experience is that everyone will tell you that their pet technique is 'green', but in most cases it seems to be a compromise. SIPs have the benefit that the OSB is a very efficient use of timber. Whist the foam does use petrochemicals, the actual quantity seems to be pretty low - the figure I've found is that the SIPs for our whole house will use only around 40 gallons in their production, which is fairly negligible in terms of the lifespan and energy savings we get in return.

Posted By: fostertomSee today's comments inhttp://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2847&page=2#Item_20" >http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2847&page=2#Item_20- SIPS are resolutely artificial, with all the health/performance implications of that.

Tom, I can't quite see how you can equate SIPs construction with sprayed polyuretheane foam?

As for health implications, the most common SIPs (Kingpsan) are urethane based so shouldn't have the off-gassing or toxicity problems of formaldehyde based insulation as I understand it. I've done some searching on evidence for health issues associated with urethane based products and can only find fact-free information from people who are selling alternative goods. Memory foam matresses have polyurethane cores and many people seem to be able to sleep on them without problem?

You also mention performance implications as though being artificial is somehow a barrier to a material working effectively. That seems disingenuous at best.

Airtight, effective use of the insulation, no Thermay Bypass, low heating bills

Jim

The Beams were installed by the main contractor, we concentrate solely on the SIPS panels. Panels are all precut in the factory, we produce drawings using a 3D cad package for the client/architect to approve. Once approved the panels are cut, floors and beams ordered and the building is erected. If you are aiming to build to a "U" value of 0.19 and air leakage of between 1-3 SIps are cost effective especially if the roof space is being used.

if you are building just to pass building regs Brick and block with a trussed roof is cheaper

Sipman

Thank you, Sipman for all the interesting info. Most tempting, in particular inpressed by the apparent strength of Sip, however, like most things in life, still not perfect. By this I mean, after all the money spent to have the sip panel build, warm as the interior and sturdy as the exterior may be, the market value of the property
does not increase. Where'as with more traditional materials, celcon blocks, stone etc. The value of the property should increase in value, often times considerably. This means a good , possibly substantial overall return for the outlay of cost. Again this causes me to vascilate on the matter. As desperate as I am to get this build up and running. I must not allow this to cloud my judgement.......

Not all sip panels are created equal!

Look at the company as much as just looking at sip as a constuction method.

They DO work well, however make sure all the design is fully buttoned up (this applies to nearly all construction methods).

SIP can be vulneralbe to bad weather during construction (don't let it get sopping wet), but once finished, should last the course if designed to do so.

make sure that the foundation/sip/existing building interfaces are robust and comprehensive.

Timber