Browse Forums Heating, Cooling & Insulation 1 Sep 09, 2015 10:49 am Undergoing some renovation work at home converting an unused roof space to bedroom. Our first floor level is built within the roof space, but currently underutilises that available space. We are having 2 roof windows installed and will create an internal wall up against the rafters in that section. leaving a short vertical wall and approx half the height of the ceiling as sloping. Kinda like this in cross section. I don't have any plans, just winging it http://i955.photobucket.com/albums/ae38/hoomac/House/Cross%20section_zpsjfzirmmg.gif Black is existing walls, blue for the windows, red for the new walls and green for a deleted wall. What sort of insulation should I use between the roof and the internal wall? The roof is at around 45degrees slope, has foil lining directly under the tiles and approx 150mm rafters. We currently have deteriorating foil insulation around the internal walls in the 'roof space' and some gold bats on the ceiling, so not very well insulated...yet! Re: Insulation for roof/wall space? 2Sep 11, 2015 12:07 pm no one? leaning towards installing roof bats with an air gap if possible between the bats and the roofing foil. Re: Insulation for roof/wall space? 3Sep 11, 2015 12:34 pm I don't know much about insulation options but we are doing an anticon blanket. Apparently it is installed on the underside of the roof so might suit your purpose? Might be worth a google anyway Re: Insulation for roof/wall space? 4Sep 12, 2015 9:15 pm With this configuration you need as much insulation as possible. If your roof tiles are dark they could get very hot (60 - 90 degrees) in summer if the roof faces north or west. This wants to conduct direct into your room. Lighter colour tiles could easily drop this by 20 degrees. (Is painting tiles / change colour an option?) Your idea of using batts while maintaining the air gap to the foil insulation (very important) is good. Ideally you should have at least R4 (and preferably more) but your available gap may make this a bit difficult to achieve. R 2.5 wall batts are 90mm thick. If you use 1 and a half batts (they should be able to be split by pulling apart) that would be 135mm and approx R 3.7. However it would cut the amount of air gap. 15 mm (150 - 135mm) is not enough air gap for the foil however if the foil is sitting above the roof battens and does not droop between the battens too much you may get enough gap. (Could consider increasing the depth of the rafter with spacer timbers nailed on.) Alternatively could consider using Foilboard (or even straight polystyrene sheet) in combination with the batts. Don't know what R value that would give you. Even with all this you may still get over heating in this room if it faces North or West. (Was over heating a problem in the original roof space room?) If the window is facing north or west this could add significant heat load into the room - it should have some sort of shutter on it to block direct sun ingress. Re: Insulation for roof/wall space? 5Sep 13, 2015 6:48 am Thanks for the reply. Fortunately this section of roof faces East. The windows will be double glazed. Will also ask the window installers what they recommend. Increasing depth of rafters is definitely an option. Re: Insulation for roof/wall space? 6Sep 13, 2015 10:01 am As per Eccles comments. Get as much and as thick as possible up there. Here are the recommended min insulation for warm temperate climates... http://i1212.photobucket.com/albums/cc455/stewiesno1/Picture1_zps3d2c5016.png ( You don't say where you are ! ) Stewie Re: Insulation for roof/wall space? 7Sep 13, 2015 10:11 am Lake Macquarie so I suppose the same as Sydney. This Reno doesn't have a deadline, budget or plans (or professional tradie) so I'll work it out better when I get the windows in! Re: Insulation for roof/wall space? 8Sep 13, 2015 2:37 pm Double glazing does not stop most direct solar heat gain (SHG) - the sun shining through the window. Should still look at the means of limiting this - even on an east window. Manufacturers might have different methods of addressing this - be it tinting or a film or a form of shutter or blind. Low-e coatings are always worth using for the increase in thermal conductance resistance and a smaller effect on lowering solar heat gain. Re: Insulation for roof/wall space? 9Sep 15, 2015 7:38 pm We had a similar situation with limited rafter space (although we wanted more like R6). We had a reflective sparking on top, air gap, a high density batt between the rafters and then 25mm of foil faced phenolic foam screwed to the underside of the rafters. We than used battens between the foam and plasterboard for a second air gap. To achieve what you are after you could just use the phenolic foam between the rafters. Every 25mm achieves ~R1.0. So you can get R4 in about 100mm. One downside is it costs more than batts. 2 7510 Hi all, Just wondering if anyone had suggestions on installing/replacing wall insulation on an external wall which doesn't have wrap, our miners cottage being constructed… 0 4940 1 19721 |