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Housing - New Build: ICF & SIP Roof

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    • CommentAuthorWeegaz
    • CommentTimeFeb 19th 2015
     
    Evening all, have been reading through a lot of comments on the forum and have learned quite a lot, but also got quite confused, but it's good to see so many knowledgable people sharing their info and helping others.

    But anyway.....

    We will be commencing our new build in the near future, currently going though planning for a change of house type, and really need some info if possible.

    Have been researching ICF construction, which seems like a worthy method of build, but would like to get some others input into this method. This along with SIP roofing panels will give an overall low U value and air tight build.

    The foundations and sub floor for a house where laid some 7 years ago before the area became green belt and the new build will use the existing foundations.

    Any info or suggestions on ICF would be welcomed.
  2.  
    I have constructed similar build, view it at www.pointoneone.co.uk I found the marriage of ICF walls, SIP roof and insulated concrete raft foundation to contribute excellent air tightness. Part 3 of the picture gallery shows the SIP roof hoisted on.
    • CommentAuthorWeegaz
    • CommentTimeFeb 20th 2015
     
    Thanks pointoneone, looks impressive and excellent blog on build.

    How did you find the ICF system? It looks like you went thicker on the external insulation, for U value i assume?

    Had you compared any of the costs of ICF and SIP to traditional build at all?

    We are getting some prices together for renewable heating at the minute, they all seem to be 'over doing' it as they recommend GSHP, UFH, Solar Thermal and MVHR, which reading forums etc, would seem excessive.

    Many Thanks
    • CommentAuthorJamster
    • CommentTimeFeb 23rd 2015
     
    We have ICF with a conventional roof. Can't comment on SIPs obviously, but for ICF:

    Make sure you understand the detail of how you will fit windows and doors into an otherwise well insulated and if done correctly very air-tight construction method. You don't say how you will finish it, but your frames may need to be 'adjusted' so you can mount them within the concrete core and still allow for any outer skin.

    You will need a SAP or more sophisticated heating / DHW assessment to allow a heating method to be spec'd - if you need one. We have a 5kw ASHP on a ~180m^2 house as we are off the gas grid - an GSHP would have been massively over spec for what we need. UFH is best friends with a heat pump a it allows a lower flow temp than radiators.

    If you build very air-tight, you will need an MVHR - no point in opening the windows or trickle vents (spec these to be left off you windows if you go MVHR) when you've spent money keeping the drafts out in the first place! The additional cost if fitted during the build should be relatively low.

    The solar thermal vs pv discussion is complicated I would think. Our DHW tank does have bosses to allow ST be added in the future; the UFH is run directly from the heat pump.

    What part of the world are you in?
    • CommentAuthorWeegaz
    • CommentTimeFeb 23rd 2015
     
    Thanks for your comments Jamster,

    We are in Northern Ireland.

    In terms of the ICF, I am really keen on the idea and am currently awaiting some prices on this method. SIP is attractive as its a modular system that is quick to erect, but gives excellent air tightness, which is what we are aiming for.

    What was your build up on your ICF? We have been looking at the Amvic system which is 65 + 150 + 65mm giving a U Value of 0.24 as a start point. I would be more interested in the 345mm overall to acheive 0.15 U value.

    Did you go for triple glazing at all?

    The external finish will be renedered with stonework cladding on certain areas.

    A supplier showed us a system where the window is mounted on the concrete skin with insulation fixed on the internal and external reveal to give an airtight seal.

    I really want to get the house priced up first to our specification and then price the heating system based on remaining budget.

    We are set on MCHR system and wood burning stove as must have's. UFH would be nice with renewable source would be ideal, budget permitting.
    • CommentAuthorJamster
    • CommentTimeFeb 23rd 2015 edited
     
    Posted By: WeegazWhat was your build up on your ICF? We have been looking at the Amvic system which is 65 + 150 + 65mm giving a U Value of 0.24 as a start point. I would be more interested in the 345mm overall to acheive 0.15 U value.


    Rhidipor did ours as we are in the NE - 100mm / 150mm / 50mm was out build up which gave 0.21; we could have had 200mm as an external element which would have been down to 0.14 but we had to draw the line somewhere and we were never confident enough that we could do away with the need for heating entirely...

    Did you go for triple glazing at all?


    We had planning conditions requiring timber sliding sash windows so this was never a go-er. I think they have a u-value of 1.4.

    We have a stone skin on ours - we used twistfix ties to link the stone to the ICF. Either push them through the ICf before its poured, or drill them in afterwards. Drilling is a bit of a ball ache.

    Re windows - get your sizes sorted early on and make sure the openings are made to fit - makes the air-tightness game much easier. We fitted insulated cavity closers into the ICF - Stone cavity.

    MVHR & stoves - get a stove with an external air feed. Also, we've noticed that the stove gets the room very warm quite quickly but that the heat doesn't travel through even an open doorway into the hall and I don't see the MVHR moving that heat very well either. Your living room or similar may be set up as 'fresh' air only and not have an extract. So they look great but my personal experience is that I'm not sure how much they would heat the whole house if that was our only heat source...

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