Insulation for Cavity Walls

Goll Mac Morna

I know that many of the posters to this forum are building or plan to build timber frame houses with maximum insulation for energy efficiency.

I however due to local circumstances (the availability of an excellent trustworthy builder) and considerations re: Passive solar design and thermal mass am going for a traditional build (cavity wall construction) or simply a house built with blocks

I have studied Zero Energy houses and Passive Houses for the last six months and was all intent on having

1 A 300mm cavity will a full fill of insulation (this would give a U-value of approx 0.13.
(the current building reg.s are demanding 0.45?? with PART L)

The thing that is putting me off the 300mm cavity is the immediate problems associated with having walls that are half a metre thick such as window boards, less internal space etc.. (although I know a man who has done this and he says it is a fantastic job) another gripe was the price of wall ties(approx €3.00 each or approx €1,600 for the whole build). and the insulation (appow €5,700 + VAT for bonded beads!!!!)

2 Anyway the next option is 150mm cavity with a full fill Board like the AEROBORD platinum (this will give an estimated U-value of 0.20)

3 Option 3 is U-value of 0.27 using boards like KINGSPAN

4 I am thinking of putting blocks 'on the flat' on the internal leaf or usinf aerated concrete blocks for their insulation capabilities (although this has to be balanced against their poor thermal store properties in comparison to ordinary concrete blocks)

Another option would be to dry line the exterior insulated wall , but then again you are messing with the thermal mass.

Another Option is "outsulation", cladding block on the outside with insulation ( i am not mad on this as the window ledges would be very thick)

I would be really grateful if someone who has recently attained low U-values using block construction could post a message here or PM me as I have been turning this over in my head for a long time.
Also if anyone could direct me to some U-value software that would be great.

kadman

http://www.kahl.net/solarch/sareadme.htm


http://www.nher.co.uk/g4.shtml

Not too sure if this is what you are looking for.

kadman

Goll Mac Morna

Thanks KADMAN for those links.
I was hoping to get some version of software similar to U-valuate???, this software allows you to input your materials used in walls and then calculates the U-value.
I came across some U-value software a couple of weeks ago, but it was taking ages to download (I have no BROADBAND ) so I had to give up.

Any ot

kadman

Hi,

I thought that I came across a study report on the web that was re assessing current regulations in relation to stability regarding increased cavity sizes.

Current standards were adopted relative to a normal 300 mm wide cavity. Due to the requirement from an energy saving point of view, and increased cavity sizes, this report reccommended a reassessment of this arrangement, as there were structural issues not covered, owing to the increased length of ties, foundation widths ect.

This was the general outline of the report, as far as I can remember, because I only glossed over it.

I have often fitted windows and doors into houses that had a breakdown as follows, 4" external block, 4" cavity, 9" cavity block, 6" internal insulated stud panel. I would not be sure of the u values though.

kadman

YAPP

If you have to go block (not TF) try and have insulation on the inside
(warm side) of the structure.

with the best will in the world, no blocklayer can fit a kingspan (or any insulation board) airtight against the outside face of the inside leaf of a cavity wall. then when the air gets inbetween the insul and block it just
takes the heat out of the block that you have tried heating.

If the insul material is on the inside of this conc leaf then theres some chance of retaining the heat..

In Meath/Kildare/Dublin areas they used to build a 9" cavity block wall and dryline the inside, alot warmer than the 4"block, 4"cavity'4"block counterparts!

Maud

Hi

I'm just back from Germany and they are using mostly outside insulation there with those red honeycombed blocks.
They say this gives very good U-values and breathability.

sas

Maud wrote:

Hi

I'm just back from Germany and they are using mostly outside insulation there with those red honeycombed blocks.
They say this gives very good U-values and breathability.

Viking House has been plugging this approach on boards for a while. His site is www.viking-house.net. The external insulation he talks about is called paroc.

Those red honeycombed blocks are poroton blocks. They are manufactured in Ireland by www.fbt.ie. If you search boards for them you'll see that some people have used them for extensions etc.

There are other companies that do external insulation solutions. www.greenspan.ie do a product called "dryvit" for example.

Insulated concrete formwork is also a slant on this, the insulation IS the external faces of the external walls. Concrete is then poured between the 2 polystyrene faces.

muffler

Goll Mac Morna wrote:

(the current building reg.s are demanding 0.45?? with PART L).........................2 Anyway the next option is 150mm cavity with a full fill Board like the AEROBORD platinum (this will give an estimated U-value of 0.20)

3 Option 3 is U-value of 0.27 using boards like KINGSPAN

External wall require a U-value of 0.27 in line with bldg. regs.

AFAIK the kingspan board affords better insulation properties over it's aeroboard platinum counterpart. Im open to correction on that though

anon1

I used a 150mm cavity and AEROBORD platinum 140mm. If doing it all again I'd use full fill pump in material like polypearl or icyene. Blocklayers do not often install insullation boards well in my opinion.

Goll Mac Morna

I would agree with you Anon re: the importance of good practice when installing insulation.
another factor is the insulation itself, we used 60mm Kingspan board in the cavity.
I was very disappointed with the quality of some of the boards (poor rebates on them i.e. the tongue and groove element was poor)
also they have a tendency to cup and bow.

Before someone asks these weren't seconds and their batch number and dates showed they were produced in 2006.

The supplier when informed took back the bad boards and gave me a couple of extra bales in lieu.

Worth bearing in mindthat probs can occur, I took it for granted that it would be a quality product with no such prob.s but like everything else when building ...worth keeping an eye on.

muffler

Goll Mac Morna wrote:

also they have a tendency to cup and bow.

Insulation panels like that are referred to as "rigid board" and should never cup and bow as you described. They were probably part of a bad batch and you were right in returning them and also right about keeping a good eye on things