Browse Forums General Discussion Re: Truss design - enough space for roof insulation 7Apr 26, 2020 3:40 pm Accessible Carpentry & Cabinets accessiblecarpentry@gmail.com accessiblecarpentry.com.au https://www.facebook.com/pages/Accessible-Carpentry-Cabinets/583314911709039 Re: Truss design - enough space for roof insulation 8Apr 27, 2020 9:37 am Yeah the drawings in red marker don't make sense to at all. You don't even have the 90mm truss chord width indicated, and no eaves at all? Even without eaves there is a slight truss overhang to allow for fascia and gutter attachment etc. It is fairly simple really, if you have eaves (especially 'cantilevered' type) you will have plenty of space for bulk insulation. Like I said previously we placed R4+R2+R2 over our top plate area so around ~360mm and still had space for air flow through the brick wall cavity --> roof. With no eaves (one east section) I could only add the R4 and one R2 roll was pretty much touching the sarking, so had to trim it down. Eaves are great for so many reasons, including insulation --------------------------------------------------------------------- Check our Homeone build blog here Re: Truss design - enough space for roof insulation 9May 09, 2020 4:09 pm darb74 You don't even have the 90mm truss chord width indicated Big assumption here. pending span, material grade and manufacturer, it could be 63mm chords (which obviously makes it worse) Regardless, what about a dropped bulkhead along the section where there isn't enough height for the insulation to be installed?? Re: Truss design - enough space for roof insulation 10May 09, 2020 7:32 pm I'm absolutely no expert, but reading a post on the My Efficient Electric Home (MEEH) Facebook group, I read that for most roofs you're not supposed to insulate over these eaves. This is because most roof space are supposed to be ventilated, to remove condensation & so mould growth. Insulating over the eaves blocks this area for ventilation. In this case you're only supposed to insulate above the internal ceiling. Hopefully others with more knowledge will chime in on this. I agree that R2.5 is inadequate for ceiling insulation. Your Home recommends R4 for Brisbane. You should put R2.5 in the walls though. Re: Truss design - enough space for roof insulation 11May 10, 2020 11:41 am ddarroch I'm absolutely no expert, but reading a post on the My Efficient Electric Home (MEEH) Facebook group, I read that for most roofs you're not supposed to insulate over these eaves. This is because most roof space are supposed to be ventilated, to remove condensation & so mould growth. Insulating over the eaves blocks this area for ventilation. In this case you're only supposed to insulate above the internal ceiling. Hopefully others with more knowledge will chime in on this. I agree that R2.5 is inadequate for ceiling insulation. Your Home recommends R4 for Brisbane. You should put R2.5 in the walls though. Anticon 60 has an R-Value of 1.3, so 1.3 + 2.5 = 3.8. Depending on color of roof, min requirement is either 4.1, 4.6 or 5.1 but the above is only insulation values, no total system. A further issue is that with the suggestion of option B you will need a cantilevered truss, which will be more expensive It's hard to comment as the photos area bit dark ( you might need a new 15 - just got one and wow ) Jokes aside, I can see one member that is cracked. I would find a… 2 2205 dimensions on your original plan are inconsistent and with accurate dimensions (including site plan, upstairs and down) i could make a proper scale drawing with furniture… 3 7497 |