Insulation beads & cavity size

Hi,

I am building a new house - is it true that you must to have a wider cavity when using insulation beads ? what is the standard cavity size ?

thanks,
CY1

the standard cavity size is 100-110 mm....

the u value you want to achieve will be directly linked to the width of the cavity.
personally i wouldnt go beyond 150mm for a cavity because all your details become very awkward at that stage, ie jambs, cills etc.

Thanks Syd.

Are you a fan of the beads in the cavity block walls on new builds ?
I am also going to dry line external walls.

Is it true you have to agree your insulation etc with a BER specialist before starting a new build ?

CY1

CubicYard1 said:

Thanks Syd.

Are you a fan of the beads in the cavity block walls on new builds ?
I am also going to dry line external walls.

Is it true you have to agree your insulation etc with a BER specialist before starting a new build ?

CY1

Click to expand...

I had a little chuckle at that one cublicyard, sorry...

Without getting into a rant, you are not statutorily required to agree insulation with a BER specialist. You are required to have your dwellig certified, and you probably have someone engaged to do this (architect / engineer). I would definatley advise you to engage a 'BER specialist' or more correctly an 'energy auditor' and take on board his advice. He will probably know a world more about insulation and energy efficiency that the guy that is actually legally required to certify the very same thing (architect / engineer).
Your certifier (architect / engineer) is currently supposed to carry out indepth mathematical calculations and analysis to confirm whether your dwelling complies with Part L regs or not (this is called the DEAP methodology).
I seriously doubt if:
1. he knows hes supposed to
2. he knows how to
3. he wants to bother.
If your dwelling is required to get a BER label, then these DEAP calculations will actually be prepared by your BER assessor. Unfortunaly, his/her calculations may actually show your dwelling to fail compliance, but these calculations by your assessor are not the legal certification, they hold no weight...

This ridiculous situation is a bit of a red rag to me at the moment.

Fair enough, this BER thing had me confused. I think my engineer needs to do a bit more in this regard.

Last Q,

Would it be better for
(a) full fill cavity block (150MM) using bonded bead insulation
OR
(B) full fill cavity block (100MM) using bonded bead insulation PLUS dry-lined external walls
?

Definately (a)....

i find with drylined walls, they tend to daub the composite plasterboard in spots rather than in a full complete circle.... this has 3 main disadvantages

1. this creates a vented cavity behind the plasterboard. There is less of an onus on builders to seal any pipes or flues properly... as in you dont worry about what you cannot see. this leads to a much less air tight construction and subsequent loss of energy efficiency.

2. this vented cavity will lead to 'thermal looping'... ie the air behind the plasterboard creates convection currents and this heated air is exhausted through bad detailing into either the roof space or out to the external as described above.

3. theres theoretically an issue with the condensation point... general rule of thumb is never to divide up your insulation. Condensation may form behind the plasterboard, and some of these plasterboards have a 'brown paper' membrane between the insulation and the plasterboard, this paper would rot easily due to mould etc, and may compromise the integrity of the board.


hope that helps...

Sydthebeat
I have decided to with the full cavity insulation 110mm cavity. I also plan to dryline inside but I'm not sure which method to use. I was thinking of using a wood fibre batton insulation system on the inside with a vapour check membrane taped directly onto the wood fibre then a 12.5 mm slab tacked onto the battons.Using this method the dew point is now directly behind the slab and not at the back of the insulation.
Is method going to work

by wood fibre do you mean a softboard system??

In this case the softboard and plasterboard is 'breathable'... assuming the plasterboard is not foilbacked..... you do not need the vapour check membrane between the softboard and the plasterboard. Any possible condensation will be drawn hydroscopically through the softboard into the blockwall. Herein lies the problem then....
The EPS bead system has an additive that restricts the movement of water across it, so the moisture in the block wall cannot go anywhere. This reduces the insulative properties of the block and may also lead to decay of the softboard.
Also, with the condensation point being behind the plasterboard and the incorporation of the vapour barrier as youve proposed, it could lead to the plaster slab being compromised, as the moistire has nowhere to go.

Another rule of thumb is either to use a complete breathable method, or a non breathable method... the non breathable method will always require a vented cavity to dry out the construction. Your systems is using a mix of both methods. I do not like to knock anyones method of construction, and i certainly do not know everything... so if theres someone with a different take on this i love to hear it.

Does anyone know how you can be sure bonded beads are spread throughout the wall cavity if you're not using any rigid cavity insulation? Surely there will be places where the beads haven't reached and you'll never know about?

In this regard would it not be better to use standard rigid insulation (against inner leaf of cavity) and bonded beads blown in as an extra insulant in the cavity?

This effectively is what I did when renovating my house. The cavity walls already had polystyrene boards (under the pre-2002 Building Regulations) and I recently had the beads blown in as extra insulation. I think that there may be advantages to this approach. First, the current polyiso boards have a better insulation value than the beads so you are getting overall better insulation than with the beads alone. Second, the beads are pumped in under pressure pushing any boards that have moved away from the inner leaf back against it. Second, although in theory, and hopefully in practice, water should not transmit across the beads, if it does the foil backed polyiso will act as a water barrier, protecting the inner leaf.
On the question of whether the cavity is completely filled by the beads, the beads are pumped in under pressure and flow around obstacles (eg wall ties) in the cavity. In my own case whereever there was a breach in the inner leaf of the cavity eg for piping, or at the top of the cavity in the attic, the beads came flowing through showing, I hope that they were filling the space.
Finally, I discovered when the installer drilled the outer walls to pump in the beads that the polystyrene boards were in fact missing in places, especially at awkward corners or towards the top of walls where the builder clearly could not be bothered to cut pieces to fit. The beads filled these gaps.

On the subject of bonded beads, I'm looking at using this method as well, can you tell me is it expensive, and who did you get to do it for you

walshey said:

On the subject of bonded beads, I'm looking at using this method as well, can you tell me is it expensive, and who did you get to do it for you

Click to expand...

My parents got this done to their existing build and it was actually quite cheap - €1100 for 3 sides of an average 2 storey house (other side had a newly built extension on it). Cost will obviously depend on cavity width and span of walls, i.e. amount of beads required to fill the cavity.

This is now a very standard procedure and almost any insulation company will provide it. Lookup "Insulation" in the yellow pages, google for Insulation, etc... and get some quotes.

walshey said:

On the subject of bonded beads, I'm looking at using this method as well, can you tell me is it expensive, and who did you get to do it for you

Click to expand...

It cost me €1300 for 1900sq ft dormer bungalow for Warmfill Silver Bead. The supplier was Kelly Insulation Wexford. I live locally.

BarneyMc said:

I'm currently looking at best cavity wall build methods for a new house build and looking at using bonded beads as the cavity insulation. Does anyone know what U values can be achieved for each of the following cavity widths…100mm, 110mm, 120mm, 130mm, 140mm and 150mm? I want to see what the optimum cavity width is regarding U value enhancement v cost.

Click to expand...

Barney I was wondering had you any luck in answering these questions on optimum cavity width with bonded beads???
Im about to start a new build and am inclined to go full fill cavity also.

Hi Musk,

Had a look in the vaults and found the details!!

"Silver Bead" 0.032-0.034 W/mk
mm U Value
100

Hi Musk,

Here's the values I was quoted for "Silver Bead" 0.032 0 0.034 W/mk:

mm U Value
100 0.27
105 0.27
110 0.26
115 0.25
120 0.24
125 0.23
130 0.22