connick159 Posted September 11, 2019 Share Posted September 11, 2019 Hi, I'm wondering if you can use SIP roof system on a non SIP build? At the moment the designer has just drawn it with trusses roof. There are a couple of Valleys and Hips in the roof. Roof to be covered with slate as a requirement from planners. We are currently building an extension to traditional cottage in Wales. Extension is block cavity construction. Pretty standard stuff as that's the "way it's done round here". Any info would be welcomed as I've searched here to see info on the SIP roof system but not found it where it's not an entire SIP build. Cheers Link to comment Share on other sites More sharing options...
PeterW Posted September 11, 2019 Share Posted September 11, 2019 What is the reason for wanting SIP..? It’s not an easy material to work with and the benefits are borderline especially on something with detail such as you’ve described. What are you trying to achieve..? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 11, 2019 Share Posted September 11, 2019 I looked at using SIPs, and one of the concerns I had was that all of the roof panel systems I looked at included substantial thermal bridges, in the form of internal rafters within the panels. The panels are also pretty heavy and difficult to manhandle, so a crane would be needed to put them in place I suspect. Link to comment Share on other sites More sharing options...
LA3222 Posted September 11, 2019 Share Posted September 11, 2019 1 hour ago, JSHarris said: included substantial thermal bridges, in the form of internal rafters within the panels. I would argue that there are significantly more thermal bridges with a truss roof due to far more timber being present? So why are SIP portrayed as worse? Surely they are an improvement on a truss in terms of a reduced amount of timber being present? Link to comment Share on other sites More sharing options...
the_r_sole Posted September 11, 2019 Share Posted September 11, 2019 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 11, 2019 Share Posted September 11, 2019 11 minutes ago, LA3222 said: I would argue that there are significantly more thermal bridges with a truss roof due to far more timber being present? So why are SIP portrayed as worse? Surely they are an improvement on a truss in terms of a reduced amount of timber being present? Depends how the insulation is placed, really. Take our roof as an example. We have 300mm deep I beam rafters hung from the ridge, with an air gap then a stud (the stud is nail plated to the I beam lower member, with an air gap). The whole space is filled with blown cellulose, so there's minimal thermal bridging (there is a very tiny amount through the OSB webs of the I beams). Putting insulation outside of a trussed roof does much the same thing. It is possible to add an additional layer of insulation to SIPs, but some of the manufacturers are a bit against this (the ones we spoke to at the time were adamant that this should not be done). If adding additional insulation to a SIPs panel, then it probably isn't any cheaper or easier than any other roof build up, I suspect. Link to comment Share on other sites More sharing options...
LA3222 Posted September 11, 2019 Share Posted September 11, 2019 1 minute ago, the_r_sole said: From memory, the sips I've seen on roofs usually have timbers at the valley/hip joins, so you have timber bridging the entire insulation area, with standard trusses you can control where the insulation sits and how continuous it is (Maybe there are other alternatives for sips roofs now as I've not done any for a couple of years) Can you not add an internal layer of insulation to eliminate any cold bridges? Much like you insulate under the rafters of a truss roof? Link to comment Share on other sites More sharing options...
the_r_sole Posted September 11, 2019 Share Posted September 11, 2019 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
LA3222 Posted September 11, 2019 Share Posted September 11, 2019 Your roof is a better design @JSHarris and I don't disagree with you. I'm picking really at your original comment which can be read as suggesting SIP suffer more from thermal bridges than a.n.other type. If you look at it from SIP compared to truss with insulation between the rafters then there is more insulation present in the SIP one and therefore better U value? (Disregarding cost comparisons) Link to comment Share on other sites More sharing options...
LA3222 Posted September 11, 2019 Share Posted September 11, 2019 3 minutes ago, the_r_sole said: Well, then you have turned a warm roof into a hybrid roof, you usually insulate between and under rafters, not between and over as you then have the danger of condensation... Sorry, might not have been clear but I meant insulate under. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 11, 2019 Share Posted September 11, 2019 1 minute ago, LA3222 said: Your roof is a better design @JSHarris and I don't disagree with you. I'm picking really at your original comment which can be read as suggesting SIP suffer more from thermal bridges than a.n.other type. If you look at it from SIP compared to truss with insulation between the rafters then there is more insulation present in the SIP one and therefore better U value? (Disregarding cost comparisons) My intention was really just to highlight that there are a lot on invisible thermal bridges in a SIPs roof panel. AFAIK, SIPs wall panels don't usually have these. Link to comment Share on other sites More sharing options...
LA3222 Posted September 11, 2019 Share Posted September 11, 2019 1 minute ago, JSHarris said: My intention was really just to highlight that there are a lot on invisible thermal bridges in a SIPs roof panel. ? I agree they do and I think the walls do as well to be fair. In my head they have much the same issues as a standard TF which has studwork at 600 centres - just less of it. However SIP cost a lot more so they may not be cost effective to take advantage of the reduction of full thickness timber within the panels ?♂️ Link to comment Share on other sites More sharing options...
the_r_sole Posted September 11, 2019 Share Posted September 11, 2019 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
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