Cavity insulation and/or internal insulation

thebagman

Howdy Folks,

Looking for some advice re the following:

Should I go for normal 100mm cavity with 60mm kingspan insulated board and 28mm insulated board on the internal wall ( builders recommendation)(option1)

Or

6" cavity to be pumped with beaded insulation and plaster finish to internal walls (my preferred choice)(option 2)

I am looking for pro's/cons to both suggestions, what bothers me most about option 1 is the 40mm left uninsulated in cavity and the possibility of gaps remaining between kingspan boards??

All feedback greatly appreciated,

Cheers

dos29

I'd go with the 6" cavity. I have an 8" cavity myself.

BryanF

bagman, what stage are you at and what has your architect/ engineer recommended?

a guy in this post http://www.boards.ie/vbulletin/showthread.php?p=71541432 has given the rough wall tickness to achieve certain U-value's. I would recommend you go for a wall U-value of below 0.15w/m2k. Ignore your builders standard approach, forget the building regs targets and go well beyond them. pre-2005 houses are now elegible for retro-fitting grants - what does that say about the direction construction methods are going..

If you must go down the block route, imo dont drylin, the builder just doesn't want to chase the block work, but you'll have to worry about every picture you bang into that wall in the future. If you haven't yet pored the foundations, make sure your architect gets a thermal bridge free design sorted and imo widen the cavity to a minimum of 200mm. this is becoming more common but you will need engineer to check.

spend that bit extra on the building envelope: floor, walls, ceiling and windows. every Euro spent here is a fraction of what you will otherwise spend on heating in the future.

AckwelFoley

There is no thermal storage capicity in insulater plasterboard. The inner leaf of a block house does. When you heat your house you also heat the innerleaf of the wall, if you then leave a door open, and then close it - the heat will be released from the wall leaf and will not take as much energy to heat back the air space again.

This is a particular arguement if you are considering renewable enery for space heating

BryanF

snyper wrote: »

There is no thermal storage capacity in insulate plasterboard. The inner leaf of a block house does. When you heat your house you also heat the inner leaf of the wall, if you then leave a door open, and then close it - the heat will be released from the wall leaf and will not take as much energy to heat back the air space again.

I'm very confused by the above, are you saying block is bad, plasterboard good, I think you'll find that having block to an inner leaf will help the building retain heat in the long run.

Having thermal mass (in this case plastered block inner leaf) in a house balances the fluctuations in room temperature/ comfort level, this is called thermal Inertia, it reduces temps in the day and releases heat at night.

In a house which will generally be occupied continuously ie everyday, it makes sense to have thermal mass, even though as you suggest initially it takes slightly longer to heat up - As houses become more air-tight and insulated with better glazing etc using thermal mass will become essential to regulate rising summer temperatures

just to clarify thermal mass means a material which can store and release heat, ie concrete, brick, stone, hemp-lime & earth etc.

snyper wrote: »

This is a particular argument if you are considering renewable energy for space heating

can you elaborate, I hope I've just picked you up wrong on this:)

imo in a new build if your going the block route, use the block. if your building in timber or some other variation then use the plasterboard.

sydthebeat

BryanF wrote: »

I'm very confused by the above, are you saying block is bad, plasterboard good, I think you'll find that having block to an inner leaf will help the building retain heat in the long run.

Having thermal mass (in this case plastered block inner leaf) in a house balances the fluctuations in room temperature/ comfort level, this is called thermal Inertia, it reduces temps in the day and releases heat at night.

i think youll find thats exactly what snyper is referring to in his last post.

BryanF

in that case apologies snyper

heinbloed

The OP asks:

I am looking for pro's/cons to both suggestions, what bothers me most about option 1 is the 40mm left uninsulated in cavity and the possibility of gaps remaining between kingspan boards??

What would you like to achieve with the renovation? Thermal energy demand before compared to after the investment?

sydthebeat

heinbloed wrote: »

What would you like to achieve with the renovation? Thermal energy demand before compared to after the investment?

its not a renovation

BryanF

bagman, what stage are you at and what has your architect/ engineer recommended?