Cavity Wall with PU Foam Insulation - Pros and Cons

[Roger Ramjet]

Are the rats capable of gnawing holes through 7.5 cm. AAC block wall?

Not to my knowledge and I have them.

Do the rats like to gnaw Polyurethane?

Yes.

How to stop rats from invading the cavity in a cavity wall?

If both walls are sealed to the ceiling there is no way they can enter.

Is it a good option to fill the cavity with PU foam?

You are defeating the purpose of having a cavity wall. Firstly the AAC blocks are their own insulator, secondly air is not a good conductor of heat.

[Khunchai]

You are defeating the purpose of having a cavity wall. Firstly the AAC blocks are their own insulator, secondly air is not a good conductor of heat.

Thank you for your information Roger.

You are right, the air is not a good conductor of heat, especially the dry air, but only as long as it remains stationary.

Since the cavity wall air gap thickness is 5 cm. in our case the cavity volume is quite large, and probably there will be some air flow as a result of convection which may degrade the heat isolating performance of the cavity wall.

Please correct me if I am wrong...

[Sometimewoodworker]

The only problem, as Fred will tell you, is that if the fill is polystyrene the rats like it.

We definitely do not want rats to come to the cavity between 2 layers of our cavity wall.

The questions arise:

• Are the rats capable of gnawing holes through 7.5 cm. AAC block wall?
• Do the rats like to gnaw Polyurethane?
• How to stop rats from invading the cavity in a cavity wall?
• Is it a good option to fill the cavity with PU foam?

1) probably yes but very unlikely to, unless there is a good food source on the other side.
2) no.
3) make access difficult to impossible.
4) it is unlikely to be cost effective or easy.

I think that double AAC block with air gap or single AAC outside and red brick or concrete block inside with air gap would be good enough. Your ROI will be low for the PU foam and I'm not sure it is easy to find anyone who can do it in Thailand, sprayed yes, injected may be not. As for other kinds of insulation in the gap condensation will reduce the effectiveness of many of them.

If you are a big user of aircon it could be that using red brick inside is better than AAC block because they will store the cold, but then you could run into problems of condensation in the cavity.

[Khunchai]

I think that double AAC block with air gap or single AAC outside and red brick or concrete block inside with air gap would be good enough. Your ROI will be low for the PU foam and I'm not sure it is easy to find anyone who can do it in Thailand, sprayed yes, injected may be not. As for other kinds of insulation in the gap condensation will reduce the effectiveness of many of them...

I am considering a double Q-CON block 7.5 cm. with a 6 cm. air gap between to be filled with 6 cm. thick PU foam panels, easy to insert, no need to inject a liquid foam.

The PU foam panels are available from Cheer System in Thailand.

Yet don't know the price (waiting for quotation), may be prohibitive.

The Return Of Investment may be 20 or 30 years, we never know...

[Sometimewoodworker]

I think that double AAC block with air gap or single AAC outside and red brick or concrete block inside with air gap would be good enough. Your ROI will be low for the PU foam and I'm not sure it is easy to find anyone who can do it in Thailand, sprayed yes, injected may be not. As for other kinds of insulation in the gap condensation will reduce the effectiveness of many of them...

I am considering a double Q-CON block 7.5 cm. with a 6 cm. air gap between to be filled with 6 cm. thick PU foam panels, easy to insert, no need to inject a liquid foam.

The PU foam panels are available from Cheer System in Thailand.

Yet don't know the price (waiting for quotation), may be prohibitive.

The Return Of Investment may be 20 or 30 years, we never know...

Please let us know any information you come up with.

[Roger Ramjet]

Since the cavity wall air gap thickness is 5 cm. in our case the cavity volume is quite large, and probably there will be some air flow as a result of convection which may degrade the heat isolating performance of the cavity wall.

Please correct me if I am wrong...

If you're using double AAC blocks and they're layed properly, where is the air flow coming from? So you have no columns, floor slab or beams between to make the cavity wall air broken into pockets? What are you going to do put holes in your slab so the air can circulate. Or holes in the wall between the pockets of air? Or are you going to leave the cavity wall open withour ring beams. Just where is the air flow coming from?
I gave my answers from experience. I've built my house of 450 square metres so I know what I'm talking about. I have no air flow racing around the house in the cavity walls to my knowledge. I do have heat coming through the glass windows and doors, but I can't totally stop all that because I couldn't find a glass man in Thailand who supplied double glazed glass with gas between, so I've just retarded it by using blinds on the inside and outside which now gives me a two degree difference in the air between the first and second floor. Today the ground floor is 84 and the second floor is 86. I can probably get that lower by a few degrees, but I'm quite happy with that at the moment.
If you need to know about convection currents in walls here's the place to go: http://www.cyberphysics.co.uk/topics/he ... y_wall.htm but the why use AAC blocks to build the house in the first place? http://en.wikipedia.org/wiki/Autoclaved ... d_concrete
This is what rats do to styrofoam: http://www.youtube.com/watch?v=sTTvd5UABQo

[Khunchai]

Is my calculation correct or not

You forgot to calculate double the labour plus double the rebar ties into the columns.

What is the standard labor cost in Isaan area to lay 1 square meter of 7.5 cm. superblock wall

[Khunchai]

I think that double AAC block with air gap or single AAC outside and red brick or concrete block inside with air gap would be good enough. Your ROI will be low for the PU foam and I'm not sure it is easy to find anyone who can do it in Thailand, sprayed yes, injected may be not. As for other kinds of insulation in the gap condensation will reduce the effectiveness of many of them...

I am considering a double Q-CON block 7.5 cm. with a 6 cm. air gap between to be filled with 6 cm. thick PU foam panels, easy to insert, no need to inject a liquid foam.

The PU foam panels are available from Cheer System in Thailand.

Yet don't know the price (waiting for quotation), may be prohibitive.

The Return Of Investment may be 20 or 30 years, we never know...

Please let us know any information you come up with.

I've come up with the following information.

ECO Foam (from Cheer System, Thailand)

Panels made of extruded polystyrene, size 2.0 x 0.6 meters.

Thickness:
• 5.0 cm (wall insulation) – THB 400.00 per piece (2.0 x 0.6 meters), THB 333 / sq.m.
• 2.5 cm (ceiling insulation) – THB 200.00 per piece (2.0 x 0.6 meters), THB 167 / sq.m.

The PDF brochure can be downloaded from here: ECO Foam data sheet

I consider using ECO Foam panels (2.5 cm) for attic insulation, is it better than Stay Cool Super Save 7.5 cm?

"Stay Cool Super Save" 7.5 cm. cost is 108 Baht per square meter.

Did anyone use "Stay Cool Super Save" for roof insulation or attic insulation? Any feedback?

It seems to be very cheap while claiming the R value of 21!

"Stay Cool Premium" is a bit more expensive at 138 Baht per square meter, having the R value of 27!

Are these R values real?

[Sometimewoodworker]

I've come up with the following information.

ECO Foam (from Cheer System, Thailand)

Panels made of extruded polystyrene, size 2.0 x 0.6 meters.

All the Rats will love you.


Fred had rats in his garage roof that had polystyrene insulation, never in his house with PU foam.

[pattayapope]

Polystrene foam is highly flamable and has been the cause of several fires over the years, it might be OK in the walls but I would certainly not use on the celings even if given it for free.

[Khunchai]

Thank you for your information.

On the other hand fiberglass roof insulation like Stay Cool is inflamable and very cheap, supposed to provide excellent thermal insulation if placed at the attic's bottom.

Did anyone use this kind of fiberglass roof insulation?

I wonder if the outer foil wrapping is strong or not...

One would not want fiberglass wool to be scattered all over the attic.

And what about rats? Do they like to gnaw fiberglass wool?

[pipoz]

Thank you for your information.

On the other hand fiberglass roof insulation like Stay Cool is inflamable and very cheap, supposed to provide excellent thermal insulation if placed at the attic's bottom.

FiberGlass_wool_Insulation.jpg

Did anyone use this kind of fiberglass roof insulation?

I wonder if the outer foil wrapping is strong or not...

One would not want fiberglass wool to be scattered all over the attic.

And what about rats? Do they like to gnaw fiberglass wool?

Where did you come across this product in Thailand? Home Mart, Globalhouse or ????

pipoz

[Mike Judd]

Fibre glass wool with foil both sides has been around for years ,usually put in-between the wood studs in the wall frame with timber structures. Come in various thicknesses from 50m.m. to 100m.m. and in rolls or packs. Also put in ceilings ,again between the timber joists. Protective clothing is usually worn as it's extremely itchy if you get the particles on the skin or the dust in your lungs. The same stuff is also made out of Rock wool now which is safer. Good quality foil has sisal impregnated inside to give it strength. But apart from the reflective qualities of the foil, anything inside is usually all the different materials that they have come up with over the years that trap air in bulk form. As far as I'am aware trapped air is the best insulation, I have seen charts that give the various materials thicknesses required to give the equivalent insulation of 50m.m. of trapped air. Maybe I have it all wrong, but that's my take on it .

[Khunchai]

Thank you for your information.

On the other hand fiberglass roof insulation like Stay Cool is inflamable and very cheap, supposed to provide excellent thermal insulation if placed at the attic's bottom.

FiberGlass_wool_Insulation.jpg

Did anyone use this kind of fiberglass roof insulation?

I wonder if the outer foil wrapping is strong or not...

One would not want fiberglass wool to be scattered all over the attic.

And what about rats? Do they like to gnaw fiberglass wool?

Where did you come across this product in Thailand? Home Mart, Globalhouse or ????

pipoz

It is available in Mega Home and Home Mart...