Green Building Forum - SIPS - different types

SIPS - different types

albacore — Sun, 11 Nov 2007 17:36:22 +0000

We are considering using SIPS for our new bungalow. It now seems that there is more than one SIP construction - some companies use EPS for the "filling", some use urethane and other manufacturers don't specify (at least on their websites) what the construction is. I have been googling and can find very little information as to the relative benefits and implications of one material over another. Does anyone know of a source of independent information on this?

Many thanks in advance for your help

SIPS - different types

tony — Sun, 11 Nov 2007 17:56:39 +0000

Dont do it -- go for some thermal mass and a real structure.

SIPS - different types

adrian hollister — Sun, 11 Nov 2007 18:12:47 +0000

Well there are two schools of thought Tony shows one of them - SIP advoates would say that the system offer's good build time, good insulation and good draft proofing and with such good levels you can reduce/remove the need for heating. They would also say that using underfloor heating with good thermal mass could provide that thermal mass. Personally I've not seen (or been aware that I've seen) a SIP constructed house in the UK but it does seem to be the predominant building material in parts of the US.

As to the materials I don't know a lot, but I've a link that I bookmarked some time ago which towards the bottom of the page goes over the different types of material. http://sipbuilding.wordpress.com/2006/12/20/foam-core-eps-xps-and-polyurethane/

Hope it helps.

SIPS - different types

tony — Sun, 11 Nov 2007 20:59:22 +0000

In my view to combine the function of structure and insulation is unwise. Alterations become a nightmare and upgrading and repairs difficult.

SIPS - different types

albacore — Mon, 12 Nov 2007 08:56:54 +0000

Adrian - Thanks for that link. It is the best description of the different types that I've seen.

Tony - I've been following your opinions on this forum for a while. While I don't disagree that we could in theory get a good level of airtightness, insulation etc with a masonry structure, it does mean that the quality of the structure is in the hands of the brickies on site who may not understand (or care) what we want to achieve. Since we have no contacts in the building industry we have no way of guaranteeing that quality, and thus have decided on the off-site construction route.

As a chartered engineer my husband is happy with the structural qualities of the SIPS panels - I must admit I thought they looked pretty flimsy at first but I am now happy to go that route.

SIPS - different types

sipman — Mon, 12 Nov 2007 22:06:51 +0000

Stick to your guns

We have have been supplying SIPs buildings for over four years, initially supplying our sister development company.

The intergral insulation and method of jointing ensures an airtight build and I would suggest that you achive on site (or very close to) the "u" value that was achived in a laboratory test, unlike many methods of site construction.

Two of our self build clients over the past year are using a wood burning stove as the only method of heating, they are also using MVHR to recycle the heat.

If you do use a conventional heating system I would install to the ground floor only.

also be aware of the potential to overheat in summer especially in the roof space

If you had concerns regarding the lack of timber in the structure 108 x100mm c24 structural timber could replace the box splines where the panles join. Structural timber would be supplied as a matter of course to all openings and areas of point load.

SIPS - different types

albacore — Tue, 13 Nov 2007 09:29:39 +0000

Thank you for your comments.

A woodburning stove is the way we plan to go with no additional heating, and with heat recovery ventilation. I still have reservations about the ability of the HRV system to distribute adequate warmth to the bedroom areas, especially as this is a bungalow construction. We are thinking about the skirting radiator system as a relatively low-disruption add-on in the event we become too decrepit to cope with the woodburner on an everyday basis, or climate change starts to look like it might turn the UK into a really cold zone.

SIPS - different types

Mark Siddall — Tue, 13 Nov 2007 18:21:13 +0000

SIPMAN said "If you had concerns regarding the lack of timber in the structure 108 x100mm c24 structural timber could replace the box splines where the panles join."

Beware of introducing more cold bridges. This could mitigate much of the thermal benefit that you hope to gain by using SIPs. Traditional TF allows for 15% cold bridging, SIPs allow less due to the nature of the technology. Surveys have shown that cold bridging tends to be nearer 20-30% in TF. Your SIPs could end up in this terratory if you are not careful. In any case I fully recomend overboading the SIP/TF with a layer of insulation to mitigate any bridging.

Mark

SIPS - different types

tony — Tue, 13 Nov 2007 18:51:07 +0000

Head plates and footers? --- seems to me may as well not use panels if insulation is needed as well -- self defeating!

SIPS - different types

sipman — Tue, 13 Nov 2007 19:44:05 +0000

Mark we have on rare occasions used timber splines, following engineering advice and then only with commercial buildings.

The majority of joints on a typical domestic dwelling would be an insulated box spline.

your figures on thermal bridging with timberframe structures are very interesting, if you also consider the dependence on best site practice to achive decent level of insulation and airtightness it would appear albacore has made a good decision.

We are in the process of designing three town house's for a developer who is intending to use Skirting heating, he reasons that with a SIP house he may require an intense heat soure for a short perod of time to get the room to a decent temperature, once at temperature the heat will not escape.

on a previous contract a developer has made provision to add a panel electric radiator should the buyers have problems with the room temperature. To date he has not had to fit any.

SIPS - different types

Mark Siddall — Tue, 13 Nov 2007 21:07:20 +0000

SIPMAN said "The majority of joints on a typical domestic dwelling would be an insulated box spline."

My concern was with the introduction of timber splines. All timber splines should be insulated, or at the very least all cold bridges should be compensated for by upping the thermal performance of the SIP by a proportional amount. So clearly establish the required performance and ensure that the design is followed through, say <0.175W/m2K. (I'd still have concerns about interstitial condensation within the timber splines where they do occur.)

Mark

SIPS - different types

sipman — Tue, 13 Nov 2007 22:14:38 +0000

Mark SIP buildings are designed to and will always contain an element of structural timber : head/soleplate,end timbers,structural posts,posts and lintels to door and window openings. The timber forms an intergral part of the structure and helps give sip buildings there structural properties. The method of construction and use of structural timber is covered in the BBA certificate.

Even in the worst case senario the amount of thermal bridging with SIPs would be far less than timberframe construction.

If we or the client have concerns regarding interstital condensation we would undertake a condensation risk analysis.