Cavity wall between garage and house insulation

[SteveMack]

Hi, So I've been trying to work out why our home office is so cold and losing heat so fast when it is warm and the last thing I've got to is the cavity wall between the garage and the office.

 

It's a block/50mm emtpy cavity/block then plasterboard however the cavity is completely open and uncovered in the garage so it mays well not be a cavity as all the cold air is getting in the cavity.

 

I'm thinking of stuffing rockwool down there and topping it with cavity closers, would anyone have a better plan, or maybe eps beads instead?  With it being a none external wall, will water still be an issue if I fully fill the cavity?

[PeterW]

EPS bead would be ideal but doubt you would get a supplier for a small area 

[Radian]

1 hour ago, SteveMack said:

will water still be an issue if I fully fill the cavity?

Depends on the proposed fill material and the condition of the cavity down at the foundation level. I've got some standing water at the bottom of my cavities at certain times of the year and I wouldn't want any fibre based insulation dunked in it. On the other hand, no problem for EPS beads. I assume your garage has a trussed roof which is why you have access to the top of the cavity?

 

The temptation here might be to fill the cavity with a bulk load of furniture-grade poly beads. The obvious issue is fire safety.

 

I'm wondering if this cavity is empty, might there be others that are also unfilled? - in which case contracting a company to inject all empty cavities would certainly be worth while. If this was the case, your stated scheme to close the cavity should still be done and before you get the cavities injected!

[SteveMack]

51 minutes ago, Radian said:

Depends on the proposed fill material and the condition of the cavity down at the foundation level. I've got some standing water at the bottom of my cavities at certain times of the year and I wouldn't want any fibre based insulation dunked in it. On the other hand, no problem for EPS beads. I assume your garage has a trussed roof which is why you have access to the top of the cavity?

 

The temptation here might be to fill the cavity with a bulk load of furniture-grade poly beads. The obvious issue is fire safety.

 

I'm wondering if this cavity is empty, might there be others that are also unfilled? - in which case contracting a company to inject all empty cavities would certainly be worth while. If this was the case, your stated scheme to close the cavity should still be done and before you get the cavities injected!

 

Correct on the trussed roof for the garage.

 

We can't have injected cavity wall sadly, we're very open aspect and get driving/sideways rain a lot which we've been told is a big no no as it can cross the injected cavity stuff to the internal walls.

 

Foundations are dry though for whatever material I choose, we've just had some work done and it's all block and beam and dry as a bone/soil/hardcore under there (un insulated block and beam sadly however it doesn't affect the other rooms as bad as the office)

 

I've seen the bags of eps beads on ebay www.ebay.co.uk/itm/325197138043

[Radian]

2 hours ago, SteveMack said:

We can't have injected cavity wall sadly, we're very open aspect and get driving/sideways rain a lot which we've been told is a big no no as it can cross the injected cavity stuff to the internal walls.

 

Did whoever told you that do a proper survey and were they considering a variety of different insulation materials available? I sincerely doubt it. Most contractors have only one kind of insulation material e.g. blown-in mineral fibre which is highly unsuitable for exposed brickwork. We had a survey done and despite being less than a mile from the sea, in exposure zone 1, there was no issue when using EPS beads.

 

This is because the beads do not conduct water across the cavity but do allow enough air to circulate behind the back of the outer leaf to assist with drying out. Have a serious look into it, the heat loss through an empty cavity can easily be halved by filling with beads.

 

Beware the beads on Ebay may well have met 1988 fire regulations, but for what purpose? Buildings or furnishings - and 1988! Today's EPS fill is graphite coated for flame retardancy.

[SteveMack]

20 minutes ago, Radian said:

Did whoever told you that do a proper survey and were they considering a variety of different insulation materials available? I sincerely doubt it. Most contractors have only one kind of insulation material e.g. blown-in mineral fibre which is highly unsuitable for exposed brickwork. We had a survey done and despite being less than a mile from the sea, in exposure zone 1, there was no issue when using EPS beads.

 

This is because the beads do not conduct water across the cavity but do allow enough air to circulate behind the back of the outer leaf to assist with drying out. Have a serious look into it, the heat loss through an empty cavity can easily be halved by filling with beads.

 

Beware the beads on Ebay may well have met 1988 fire regulations, but for what purpose? Buildings or furnishings - and 1988! Today's EPS fill is graphite coated for flame retardancy.

 

Well spotted, I read as 1998   Will hunt for the graphite ones instead

 

We only have 50mm cavities (1990 house) and apparently even the eps beads can get wet and transmit the water across that thinner cavity.  75-100-150 would work with eps but apparently not 50mm. 

 

We're zone 2 it looks.  I might get another contractor out to look at it, I've just gone off what we were told when we bought the house.

[Radian]

Have a read through what thegreenage say about EPS. The beads are naturally water repellent and even in a 50mm cavity, there will be dozens between the inner and outer leaves so water has to transfer around each sphere to make the journey across. It's like having a series of drip mouldings and one of those is usually enough to stop water transferring horizontally. Another analogy is thatch. Each reed in the bundle directs the rain down the length of the roof an not into the roof. It's one of those phenomena where statistics provide you with the goods.