Ceiling insulation

[Possum]

The radiant barrier foil reflects the radiant heat back up. If placed a few inches under the metal roof it keeps the attic space cooler. If placed on top of the ceiling in the attic it of course doesn't keep the attic cooler but it keeps the interior ceiling from being heated by radiant heat. In both cases it aids in lowering the heat transmission to the interior of the house. It's so inexpensive it's just makes sense to use it.

[Clermont]

We’ve just insulted 3 houses in a subdivision and the builder put the insulation as close to the roof as possible and held it there with strip’s of builder aluminium strips pop riveted to the gables, silver paper to the roof, no arguments from me.

[hk blues]

3 hours ago, Greglm said:

The radiant barrier foil reflects the radiant heat back up. If placed a few inches under the metal roof it keeps the attic space cooler. If placed on top of the ceiling in the attic it of course doesn't keep the attic cooler but it keeps the interior ceiling from being heated by radiant heat. In both cases it aids in lowering the heat transmission to the interior of the house. It's so inexpensive it's just makes sense to use it.

My though was it would also reflect the cooler air back down and stop it escaping into the roof space. 

[Jollygoodfellow]

On 3/29/2023 at 9:24 PM, Viking said:

The company I bought it from said it was more effective just putting it on top of the ceiling, but I am not really sure that is true.

In Australia, the foil is common and usually fitted when building a new home. It is rolled out over the rafters then the roof sheeting is placed on top. But in your case that means taking the roof off.

Another method to insult a small space is to blow in insulation foam or insulation material but I doubt in anyone has a blower type set up here.

[Viking]

10 hours ago, hk blues said:

I assume it works both ways i.e. prevents heat from entering the roof space and also keeps the cool air below where it belongs?   

I don't think so. It's designed to reflect radiant heat. If you want to stop your cold air to escape up through the ceiling you probably need insulation like rockwool or something similar.

2 hours ago, Clermont said:

We’ve just insulted 3 houses in a subdivision and the builder put the insulation as close to the roof as possible and held it there with strip’s of builder aluminium strips pop riveted to the gables, silver paper to the roof, no arguments from me.

The radiant barrier need an air gap to work. It doesn't work if it is in contact with the roof. If it's the type with foam on the back it may work, but I am not sure?

1 hour ago, hk blues said:

My though was it would also reflect the cooler air back down and stop it escaping into the roof space. 

Regular insulation is probably better for that situation.

[Viking]

1 hour ago, Jollygoodfellow said:

In Australia, the foil is common and usually fitted when building a new home. It is rolled out over the rafters then the roof sheeting is placed on top. But in your case that means taking the roof off.

Another method to insult a small space is to blow in insulation foam or insulation material but I doubt in anyone has a blower type set up here.

I actually got a quotation for insulation of the ceiling, from the same company selling me the radiant foil. 110 sqm of 5 cm Rockwool would cost me 110k pesos.

The radiant barrier was around 6500 pesos.

I am curipot, so I went with the foil, 😂

[Dave Hounddriver]

All this talk about radiant barriers sent me scurrying for my Google search button.  What I found interesting, in this particular link, is the picture that shows radiant barrier in so many places but NOT lying flat on the ceiling joists.

https://www.energy.gov/energysaver/radiant-barriers#:~:text=Radiant barriers and reflective insulation,must face an air space.

[Possum]

10 minutes ago, Dave Hounddriver said:

All this talk about radiant barriers sent me scurrying for my Google search button.  What I found interesting, in this particular link, is the picture that shows radiant barrier in so many places but NOT lying flat on the ceiling joists.

Sure, they could put it higher so they did so. If that is not possible its effective putting it on the top of the top of the joists holding the ceiling. What is shows in the pphoto appears to be insulation with a radiant barrier on one side which is available here. I have a heat gun and placed radiant barrier on top of insulation in the ceiling of one half of a room of a house on Florida. The heat gun indicated the interior ceiling temperature where the radiant barrier was installed was 3-5 degrees F lower than the other half.

[Possum]

24 minutes ago, Viking said:

I actually got a quotation for insulation of the ceiling, from the same company selling me the radiant foil. 110 sqm of 5 cm Rockwool would cost me 110k pesos.

I ran into the same thing. There are lower cost blown insulation products than rock wool available just not here in the Philippines unfortunately. The foil works, not as well as insulated foil but it's a cheap money saver.

[Viking]

I can now give an update on our installed radiant barrier foil.

It's working!!!

A significant difference. When one room was done I put my hand to the ceiling and it was noticeably cooler than than in the room without the radiant barrier.

Before it was a similar feeling as an infrared heater, if you got close to the ceiling. That feeling is now completely gone 

I am happy and my wife is even happier, because she suffers more from the heat than I do.