Insulate a flat roof

garlad

Hi,
Moved in to a house with a badly done kitchen extension out the back of the house. Gets very cold in Winter, presumably coz theres no insulation.
Gonna knock it in 5 or so years time, but for the time being, any cheap way I can add some kind of insulation.
Was thinking foil backed plasterboard put directly onto existing ceiling for a start.
Any thoughts?

Mellor

garlad wrote:

Hi,
Moved in to a house with a badly done kitchen extension out the back of the house. Gets very cold in Winter, presumably coz theres no insulation.
Gonna knock it in 5 or so years time, but for the time being, any cheap way I can add some kind of insulation.
Was thinking foil backed plasterboard put directly onto existing ceiling for a start.
Any thoughts?

Foil backed plasterboard is not an insulation, it is to cope with higher levels of moisture in certain areas of a house. If its a kitchen extension the plaster board should already to foilbacked. In terms of retrofitting insulation, the roof will be the easiest point to do this. If you think this is a weak point of the extension then I would defo reccommand it. Depending on the type of roof you have the correct way to insulate will differ. Do you know if it is a warm or cold roof. What way is it insulated now?

ircoha

Another idea, working from the inside, would be to buy some insulated board eg 37mm insulation on 12.5 mm pb and screw them up to the existing ceiling joists.

Tape and fill the joints, prime and paint and wait till u doze.

What about the walls/floor?

garlad

Thanks for the reply guys.
Reckon its a warm roof.
Kitchen extension has no insulation on walls. Floor is chipboard (I know!) raised about 3 feet above ground. Ceiling lokks like a normal spackled ceiling, doubt if insulated at all.
ircoha, your idea sounds like the one I was trying to explain. Basically looking for a cheap option that will only be around for 5 years or so, as I plan to pull down extension eventually.

Rongil

I am busy renovating a kitchen with a lousy flat roof and no insulation. I phoned an insulation guy and he said he would pump insulation into the ceiling/roof cavity with 6 inches of blown insulation. This is not permanent, but sounds like foam pellets, so when I re-roof my flat roof, the insulation stays where it is. Cost about €150.00 per room, so very cheap as well.

gud luck

ircoha

garlad wrote:

Thanks for the reply guys.
Reckon its a warm roof.
Kitchen extension has no insulation on walls. Floor is chipboard (I know!) raised about 3 feet above ground. Ceiling lokks like a normal spackled ceiling, doubt if insulated at all.
ircoha, your idea sounds like the one I was trying to explain. Basically looking for a cheap option that will only be around for 5 years or so, as I plan to pull down extension eventually.

No prob, pm me if u need any more info.
You might consider doing walls also

ircoha

Rongil wrote:

I am busy renovating a kitchen with a lousy flat roof and no insulation. I phoned an insulation guy and he said he would pump insulation into the ceiling/roof cavity with 6 inches of blown insulation. This is not permanent, but sounds like foam pellets, so when I re-roof my flat roof, the insulation stays where it is. Cost about €150.00 per room, so very cheap as well.

gud luck

when u re-do the roof plan for putting more insulation as the "blow-job" can be very iffy.

Mellor

I'd go for fibreglass blown insulation as opposed to EPS beads. As they appear much more stable, less loose in a way. But look into both if cost is an issue as I don't know prices on either, but I can't imagine there being much difference.

garlad

Rongil, you have a number for this guy? Can you PM it to me?

rooferPete

Hi,

A question you may want to ask is how does the insulation get past any bridging fixed between the roof joists ?

A lot of extensions with flat roofs have pieces of timber fixed between the joists for strength, these timbers are usually the same size as the joists, so blowing any insulation will only extend as far as the first bridging piece leading to half the roof space being insulated at best.

If the roof is strong enough you still have the option of fitting 50 mm Styrodour insulation on top of the roof finish and using 50 mm of ballast.

.

Carpenter

rooferPete wrote:

Hi,

A question you may want to ask is how does the insulation get past any bridging fixed between the roof joists ?

A lot of extensions with flat roofs have pieces of timber fixed between the joists for strength, these timbers are usually the same size as the joists, so blowing any insulation will only extend as far as the first bridging piece leading to half the roof space being insulated at best.

If the roof is strong enough you still have the option of fitting 50 mm Styrodour insulation on top of the roof finish and using 50 mm of ballast.

.

Hi pete
Nice 2 see you back around these parts

rooferPete

Hi Carpenter,

Taking a little time off work

.

garlad

rooferPete wrote:

Hi,

If the roof is strong enough you still have the option of fitting 50 mm Styrodour insulation on top of the roof finish and using 50 mm of ballast.

.

Hey RooferPete,
Insulation external on top of roof? Or internal screwed onto ceiling? External is felt finish. What do you mean by ballast?

Mellor

External insulation is very common, and alot easier to do right. for a retro-fit job, would look at this option.

As for the blown insulation, I imagine that to get around the bridging they just have to use extra holes. With a bit of luck the OP will have herringbone bridges.

rooferPete

Hi garlad,

Fitting insulation on top of the roof is a system used more on industrial and commercial roofs but works on most flat roofs.

Ballast is usually 50 mm of chippings to hold the insulation in place, that is why you check to ensure the roof will take the extra weight.

Based on the guide spec posted earlier I doubt herringbone bridging would have been used, any blown insulation jobs I have come across were carried out at by drilling the facia or soffit not the roof.

.