Browse Forums Heating, Cooling & Insulation Re: Roof insulation and building code 12Aug 24, 2020 9:04 am Coldallthetime The insulation contractor came out along with the rep from the insulation manufacturer. The rep agreed its not the correct height and something has gone wrong so hes gone back to talk to his boss but he thinks that they will lay another layer of R1.5 or R2 over the top, Does this seem like an ok thing to do? Is R4 that is compressed to R2 thickness still effectively R2? No one can still give me a definite answer regarding whether I am correct about it should be R5 due to the dark roof so I will keep going with that. Incidentally I was up in the roof last week on a cold day but the sun was out and the inside of the metal roof was hot to the touch and the air was hot as well, it must have been over 30C up there even though it was probably about 15C outside Thanks ahhh, definitely not to spec if compressed. When you install batts, manufacturer guidelines require you to 'activate' the batt...which is basically getting it out and tapping it on all sides to get it to fluff up. If you compress it it loses air gaps and therefore R value. But having said that, I placed 2 layers of batts on our perimeter (R4 + R2) and the overall heights were fairly close to full spec when you add both together so I don't think if done carefully it is too bad. The main thing to be honest is the quality and care of the installation. Avoiding and gaps is important as studies have shown that even 5-10% gaps can reduce the effectiveness by up to 50%! If it is no cost to you I would get them to install the batts, paying particular attention to the outside perimeter area, as these zones typically leak the most heat/cold. If you still want to top it up maybe later down the track then I would suggest getting someone in to blow in cellulose over the top and it does a great job of filling in any gaps as well. **Anyhow back to your originaly question one way to check your install is to look up the specs for 'thickness (mm)' for your batt type and you can then easily measure the overall to see how compacted it is. --------------------------------------------------------------------- Check our Homeone build blog here Re: Roof insulation and building code 13Sep 21, 2020 1:53 pm They are going to put an extra R2 layer on top, the original stuff is only around R2.5. Afterwards I think I will do as you say and get some loose fill stuff put it. Is it possible for me to buy bags of that and do it myself? I've been looking but could only find people who come and do it for you. Thanks for your help Re: Roof insulation and building code 15Sep 21, 2020 3:43 pm Because there are still many little gaps around the air con, vents, joists etc etc Re: Roof insulation and building code 16Sep 21, 2020 4:00 pm Coldallthetime Because there are still many little gaps around the air con, vents, joists etc etc When you apply roll, you generally would have to seal with polyutherane the gaps around penetrations. Small hard-to-seal type of gaps are still okay, they won't be really adding significantly to the overall thermal loss/gain (may be up to 5% tops). You will certainly lose much more than that (30%-50%) by placing batts between joists due to thermal bridging effect. Re: Roof insulation and building code 17Sep 21, 2020 4:06 pm I'm a little confused... So where does the roll/blanket go? over the joists? I had wondered about the joists not having any insulation over them at all, I was thinking ideally batts up to the height of the joists and then some more insulation, batts or whatever options there are, over the top. Re: Roof insulation and building code 18Sep 21, 2020 4:10 pm Over the joists, correct. Insulation in batts will certainly add extra points. But what about downlights, electrical cabling, etc.? Make sure you do not create fire hazard. I would be only running electrical cables in conduits and would need to cover downlights with special domes in that case. Re: Roof insulation and building code 19Sep 21, 2020 4:12 pm OK right, so is the roll/blanket the same as batts just not cut up into pieces that fit between the joists or made of different materials? Re: Roof insulation and building code 20Sep 21, 2020 4:19 pm Similar or same materials. It is continuous insulation, hence, reduces thermal bridging. You can also run 2 of them on top of each other for better insulation. https://pricewiseinsulation.com.au/prod ... il-facing/ Hi All, see above image. The required setback from the rear boundary in my case is 5m, as you can see the shape of the site and location of the boundary is slightly… 0 8451 CDC Housing Code 3 When to apply Floor Area external face of wall vs Gross Floor Area internal face of wall. Reading thru CDC Housing Code 3, lets take a lot 915sqm.… 0 16558 |