Roof Insulation To Reduce Temperature

[torrenova]

We've had a lot of information recently about roof insulation and I want to see if I have understood it and then try to get an idea of what to do in my situation.

In Buriram the missus bought a two story semi detached house. Doors all open downstairs so we run fans but upstairs (2 bedrooms) gets incredibly warm from sunrise and even well past sunset. In this season, I guess it is just too hot all the time.

An aircon is coming (when I sort out which one - another thread) but I think a lot of the problem is the roof which is nearly certain some cheap tiles and a suspended styrofoam ceiling below. A fair air space to feed heat back into the rooms. Poor wall construction I can do nothing about but the roof insulation does interest me greatly.

Now if I understand correctly, some sort of aluminium or shiny surfaced membrane should be placed at some distance from the tiles, shiny side downwards. I don't know whether there are air bricks (I doubt it) so please advise on whether to put some of those in.

So if I am right, just what is the thing to buy ? I like a full range of costs versus benefits where I decide on the cost benefit analysis. Anything to avoid ?

So what is the cost and can Somchai do this (I know, don't ask a silly question). Just how do you install it and joint the sheets ?

Please leave any comments to assist.

[spud1]

Has you live in a hot climate any installation of foil backed insulation should be laid with the aluminium side facing externally,thus preventing the penetration of heat internally.

[torrenova]

Has you live in a hot climate any installation of foil backed insulation should be laid with the aluminium side facing externally,thus preventing the penetration of heat internally.

I would have said that but recent threads seem to indicate otherwise. I don't know the physics of it but am trying with the wdndow shield in the car which is gold on one side and silver on the other.

[Artisi]

The point to which side of the reflective aluminium sheeet should be has been discussed to its death over the past week or so - check a few of the recent posting about roof insulation and then do some research on the internet where you will find that all research confirms that the shiny side of the reflective aluminium foil sheet should be installed DOWN for the maximum long term efficient method of reducing heat transfer into your roof space.

[fremmel]

The basic thing you're trying to do with attic insulation is to keep heat from entering your living space through the ceiling. If you're opening the windows that means you'd like the ceiling to be the same temperature as the outside air. So you have to get the attic the same temperature as the outside and a good way to do that is with the foil hung from the rafters with the shiny side down AND good attic ventilation. Without the ventilation the attic is still going to heat up, just slower. If you don't have ventilation in the attic then you'll also get some benefit from putting fiberglass batts on top of the ceiling to stop the heat from coming through. In the rental houses I lived in before I built my house I didn't hang foil but I would put in ceiling insulation in the rooms I used most during the day. Even without the AC on you could tell a difference walking from a room with ceiling insulation into a room without.

If you are going to be using air conditioning, then you'll get benefit from ceiling insulation even if you have a ventilated attic with foil. Ceiling tiles or sheetrock have very little resistance to heat flow so as you cool your room lower than the attic temperature you'll still get heat coming in through the ceiling.

As for cost/benefit analysis you'll have to do that yourself because there are too many variables and some intangibles. To me it was worth it, even in the rental houses, because it was less than a couple of thousand baht per room and I felt like I got payback within a year. Besides the energy savings from not having to use the AC as much the rooms were more comfortable when the AC was on. With a hot ceiling, even if the AC cools the air down, you still feel the heat radiating from the ceiling and it's just not as comfortable.

[torrenova]

I think any CBA has to include far more than money as comfort is much improved when done properly as know from some places I know.

[Swelters]

The basic thing you're trying to do with attic insulation is to keep heat from entering your living space through the ceiling. If you're opening the windows that means you'd like the ceiling to be the same temperature as the outside air. So you have to get the attic the same temperature as the outside and a good way to do that is with the foil hung from the rafters with the shiny side down AND good attic ventilation. Without the ventilation the attic is still going to heat up, just slower. If you don't have ventilation in the attic then you'll also get some benefit from putting fiberglass batts on top of the ceiling to stop the heat from coming through. In the rental houses I lived in before I built my house I didn't hang foil but I would put in ceiling insulation in the rooms I used most during the day. Even without the AC on you could tell a difference walking from a room with ceiling insulation into a room without.

If you are going to be using air conditioning, then you'll get benefit from ceiling insulation even if you have a ventilated attic with foil. Ceiling tiles or sheetrock have very little resistance to heat flow so as you cool your room lower than the attic temperature you'll still get heat coming in through the ceiling.

As for cost/benefit analysis you'll have to do that yourself because there are too many variables and some intangibles. To me it was worth it, even in the rental houses, because it was less than a couple of thousand baht per room and I felt like I got payback within a year. Besides the energy savings from not having to use the AC as much the rooms were more comfortable when the AC was on. With a hot ceiling, even if the AC cools the air down, you still feel the heat radiating from the ceiling and it's just not as comfortable.

Agree with all this.

Swelters