Pump the cavity?

2500w

We have a 2 100 mm blocks with a 100 mm cavity.
60 mm insulation board in cavoty attached to inner leaf.
House completed one year ago.

The walls were never dry lined and we regret this. Would it make sense to pump the cavity to improve the insulation? Is there a suitable product?

Regards

muffler

I'll move this to the main C & P forum.

YourAverageJoe

My worry would be dampness reaching the internal wall.

Heatherview

Hi 2500W
What is the reason for your regret with drylining? if cavity wall insulation is fitted correctly,your inside block that is plastered acts like a big storage heater, retaining heat for a long period after heating is turned off, and a certain amount of heat will be transmitted into your room after heating is turned off. See detail

muffler

Heatherview wrote: »

Hi 2500W
What is the reason for your regret with drylining? if cavity wall insulation is fitted correctly,your inside block that is plastered acts like a big storage heater, retaining heat for a long period after heating is turned off, and a certain amount of heat will be transmitted into your room after heating is turned off. See detail

I think the OP is asking if there is a "pumped insulation" product available for additional insulation of the cavity walls of his house

RKQ

I would not pump anything into a cavity with insulation already installed. There is probably foil backed highh density insulation in the cavity.

Consider upgrading the attic to 300mm plus to compensate for the walls.

mickdw

Id say you possibly have draft problems OP. If everything was done correctly with the partial fill insulation, there would be nothing to regret to be honest.
Dormer houses in particular are often not sealed properly. What type of house do you have?

Quazzie

Most pumped insulation companies require a minimum cavity within the wall for their product to be effective. I don't think 40mm will eb enough. If you take into consideration that some of the boards might be moved away from the cavity then this could be in fact less. I don't think there will be enough clear space for the reasonable travel of the beads when pumping. While haing the walls pumpped will increase the insulative effect of the walls it would be patchy at best, and at worst encourage ingress of water to the inner leaf

gizmo555

Quazzie2002 wrote: »

Most pumped insulation companies require a minimum cavity within the wall for their product to be effective. I don't think 40mm will eb enough.

According to the Agrément Board certificate I have seen for one bonded pearl product, 40mm is the minimum gap required.

Quazzie2002 wrote: »

While haing the walls pumpped will increase the insulative effect of the walls it would be patchy at best, and at worst encourage ingress of water to the inner leaf

If this is so:

(a) Why do these products have Irish Agrément Board certification?

(b) Why is the government now giving grants to retrofit pumped cavity insulation?

Just curious . . .

Quazzie

gizmo555 wrote: »

According to the Agrément Board certificate I have seen for one bonded pearl product, 40mm is the minimum gap required.

Apologies. I might be wrong. The particular company I used stated 50mm as a minimum. That could (probably is) only specific to that particular company.

gizmo555 wrote: »

If this is so:

(a) Why do these products have Irish Agrément Board certification?

(b) Why is the government now giving grants to retrofit pumped cavity insulation?

Just curious . . .

They do work, particularly well with cavities that are totally without insulation (as mine was), however I think when adding it to a cavity already with pre-installed insulation I personally think it can be patchy. I have been told this by a rep for a few companies too, but this might have been to try to get my sale because they knew mine had none.

I think that its possible to make anything work in theory, its taking bad workmanship into consideration that I think is the factor. Any defects in the insulation already installed is going to have a proportionate effect on the pumped insulation. In the OP's case a 40mm cavity could be as low as 20mm taking this into consideration and I think that would be problematic.

It might also be noted that combining two insulations of different set ups can have a negative effect but this I'm totally clued up on so maybe someone else can comment on this.

gizmo555

On the specific question of the risk of water penetration, here's what one Agrément board certificate says:

4.2 LIQUID WATER PENETRATION
4.2.1 Test data obtained by the IAB confirms that a
masonry wall incorporating [A Bonded Bead Product] and built to the
requirements of IS 325: Part 1: 1986, will not
transmit water to the inner leaf.
4.2.2 Test data obtained by the IAB also demonstrates
that [A Bonded Bead Product] Cavity Wall
Insulation material does not absorb water by
capillary action. Water which penetrates the outer
leaf of the wall will drain down the cavity face of
the outer leaf. When the product is used in
situations where it bridges the dpc in walls,
dampness from the ground will not pass through,
provided the cavity is taken down to at least 150
mm below the level of the lowest dpc.
4.2.3 [A Bonded Bead Product] Cavity Wall Insulation,
when used in accordance with this Certificate,
presents no significant risk of water penetration.

Every other certificate for these types of product I have looked at, for both bonded bead & rockwool, contains a similar section. I suppose the moral is, ensure whatever product you are considering has Agrément board certification. You can search these here:

http://www.nsai.ie/index.cfm/area/page/information/CertificateSearch

On the question of workmanship, the certificates contain useful information on how these products should be installed and one could check with one's prospective supplier that they will install in conformance with the methods in the certificate. You are right that workmanship is crucial, especially in a situation like this where you can't actually see the finished job! Try to get a supplier with good recommendations and/or references and don't go by price alone.

Quazzie

gizmo555 wrote: »

On the specific question ... don't go by price alone.

I agree 100%, and I probably should add that some of the suppliers I checked out probably weren't IAB certed and thats why they didn't discard water ingress. Good post gizmo

RKQ

Just a point as regards minimum clear cavity of 40mm or 50mm. While there is a minimum width required, I'd double any IAB cert gives a u-value for 40mm thickness of insulation. Each manufacturers product would be tested with 100mm thickness.

Using half the thickness of insulation does not mean you will get half the u-value!

I would not recommend pumping either bead or rockwool into a cavity wall with facing bricks, brick quoins or brick archs.

2500w

Thanks for all the replies.

It is a dormer.

We are disappointed with the performance of the UFH system and suspect that heat is escaping between the floor screed and the walls. I am not sure that perimeter insulation was installed between the floors and wall. Therefore I was seeking to compensate for this unfortunate omission by the builder.

Not too many people recommending the pumping option so I will probably leave that. I wonder how big a factor is this perimeter heat loss and whether it is repairable. I have lots of wool in the attic (8 inches I'd say) and 5 inch rigid insulation boards in the sloping ceilings. That I am sure of. No curtains up yet but I'm working on it.

gizmo555

RKQ wrote: »

Just a point as regards minimum clear cavity of 40mm or 50mm. While there is a minimum width required, I'd double any IAB cert gives a u-value for 40mm thickness of insulation. Each manufacturers product would be tested with 100mm thickness.

Using half the thickness of insulation does not mean you will get half the u-value!

A random check of a couple of certs shows that they give U-values for a range of cavity widths from 50mm to 130mm. In the couple I looked at, the U-values for 50mm (the lowest cavity width tested) are in fact slightly better than half the performance of 100mm.

(1) 50mm = 0.58W/(m2K), 100mm = 0.34W/(m2K)
(2) 50mm = 0.59W/(m2K), 100mm = 0.34W/(m2K)

RKQ

2500w wrote: »

We are disappointed with the performance of the UFH system and suspect that heat is escaping between the floor screed and the walls. I am not sure that perimeter insulation was installed between the floors and wall. Therefore I was seeking to compensate for this unfortunate omission by the builder.

I wonder how big a factor is this perimeter heat loss and whether it is repairable.

Repairable? - Difficult and costly to rectify.
Depends on exact position of pipe and your tolerances for dust! It might be possible to remove skirting and floor covering, cut a 150mm deep channel circa 30mm wide. It would be alot of work.

Alternatively, insulation could be fitted in the cavity, along the floor depth. A retro-fit cavity tray might be used to prevent water build up. Costly to remove lenths of external blockwork wall but less disruptive to interior.

RKQ

gizmo555 wrote: »

A random check of a couple of certs shows that they give U-values for a range of cavity widths from 50mm to 130mm. In the couple I looked at, the U-values for 50mm (the lowest cavity width tested) are in fact slightly better than half the performance of 100mm.

(1) 50mm = 0.58W/(m2K), 100mm = 0.34W/(m2K)
(2) 50mm = 0.59W/(m2K), 100mm = 0.34W/(m2K)

That was quick, well done!
As I said above, half the thickness is not half the u-value. QED.

Good luck with 0.58W/(m2K):D - well worth the expense and risk :eek:
50mm of aeroboard will make such a differenced - I think not.

Well done to all contributers, this is quite an interesting thread.

gizmo555

RKQ wrote: »

That was quick, well done!
As I said above, half the thickness is not half the u-value. QED.

No, as you can see in these examples, it is better than half the U-value.

RKQ wrote: »

Good luck with 0.58W/(m2K):D - well worth the expense and risk :eek:
50mm of aeroboard will make such a differenced - I think not.

Not sure what you are saying here - do you think extra cavity insulation with a performance 0.58W/(m2K) is a worthwhile improvement or not, given a net cost of around €800 to €1,000 after the new grant is taken into account? What "risk" do you mean?

2500w

We have photos and some of the UFH pipes go right up against the wall!

Could repairing via the cavity reduce heat loss significantly?
The existing cavity insulation begins at subfloor level so how would the extra stuff go in?

RKQ

If you are sure the cavity insulation goes down to sub-floor level, then thats good. You have some insulation but are still heating the blockwork!

Internal insulation along the side of the floor is definitely required and would improve your situation. It can be retro-fitted but its not easy to do, especially if the pipes are so close to the block work.

It a difficult one to resolve.

bogman

RKQ wrote: »

I would not recommend pumping either bead or rockwool into a cavity wall with facing bricks, brick quoins or brick archs.

Question here, would it matter if they were concrete or clay bricks, would concrete be more impervious to water?

RKQ

Clay brick soaks water. Concrete brick soaks water.

However, a perfectly smooth concrete brick might not soak water as badly. The smooth unaeratered surface might not be as bad.

Either way I wouldn't recommend filling the cavity behind brick.

Quazzie

RKQ wrote: »

Clay brick soaks water. Concrete brick soaks water.

However, a perfectly smooth concrete brick might not soak water as badly. The smooth unaeratered surface might not be as bad.

Either way I wouldn't recommend filling the cavity behind brick.

Why not RKQ? Where's the risk?


Just kidding