Cavity Insulation - Blown-in bead + Kingpsan board

fitzie79

I have started to build a bungalow and have a standard cavity with 60mm kingspan boards in the cavity. I have decided to install a HRV system and in order to make my masonry build as air-tight as possible I am looking at different methods.

I came across an article recently on Construct Ireland where they recommended the use of blown-in beads as a method of improving the air-tightness of the building. It seems like this would help as it reduces the amount of air that can flow in the cavity and should also have the added benefit of improving the insulation. Is there any draw backs or problems to using the blown-in bead combined with the Kingspan boards?

Also, I have drylining boards on all the external walls of the house. My understanding is that these will be fixed to the wall using daubs. I have also read that applying a wet plaster finish is a good method of achieving air-tightness. Is it standard practice to have a scratch plaster finish on the wall before putting on the drylining boads or is this something I would need to ensure the builder does?

sydthebeat

fitzie79 wrote: »

I have started to build a bungalow and have a standard cavity with 60mm kingspan boards in the cavity. I have decided to install a HRV system and in order to make my masonry build as air-tight as possible I am looking at different methods.

I came across an article recently on Construct Ireland where they recommended the use of blown-in beads as a method of improving the air-tightness of the building. It seems like this would help as it reduces the amount of air that can flow in the cavity and should also have the added benefit of improving the insulation. Is there any draw backs or problems to using the blown-in bead combined with the Kingspan boards?

Also, I have drylining boards on all the external walls of the house. My understanding is that these will be fixed to the wall using daubs. I have also read that applying a wet plaster finish is a good method of achieving air-tightness. Is it standard practice to have a scratch plaster finish on the wall before putting on the drylining boads or is this something I would need to ensure the builder does?

as you have drylining boards on the external walls you have already compromised any hope of good air tightness.
In a block build the main air tightness layer is the plaster finish on the block. You now have an unplastered blocks under your drylining boards.. you will have gaps all over the place, such as at pipe projections, at electrical fittings, at openings, especially window boards...

your only hope is to seal up as may of these areas as possible with caulk. Flexi mastic sealant will be compromised eventually.

pumping your cavity "may" improve your air tightness slightly, but it will not alone give you a house air tight enough to make a HRv system viable.

you need to engage an air tightness specialist (not just a BER assessor). you need to get an air tightness done as is.. .the areas of air infiltration need to identified and solutions specified. Then, after these solutions have been incorporated, you need to get a second air tightness test done....
In order for a HRV system to be in any way viable you should aim for an air tightness result of 5 or better, preferrably lower.....

Davy

fitzie79 wrote: »

I came across an article recently on Construct Ireland where they recommended the use of blown-in beads as a method of improving the air-tightness of the building. It seems like this would help as it reduces the amount of air that can flow in the cavity and should also have the added benefit of improving the insulation. Is there any draw backs or problems to using the blown-in bead combined with the Kingspan boards?

Make sure it cant come in contact with electrical cables, it reacts with the pvc insulation.

fitzie79

sydthebeat wrote: »

as you have drylining boards on the external walls you have already compromised any hope of good air tightness.
In a block build the main air tightness layer is the plaster finish on the block. You now have an unplastered blocks under your drylining boards.. you will have gaps all over the place, such as at pipe projections, at electrical fittings, at openings, especially window boards...

hi sydthebeat - your point about the drylining being on the blocks is one of the points i was concerned about. i am taking it from your answer that it is not standard practice for the builder to put a scratch plaster layer under the drylining?

if i get him to do this would this substantially improve the air tightness?

i intend to get the air tightness test done after first fix is completed to fix any major issues before the final plaster finish on the wals

ardara1

fitzie79 wrote: »

hi sydthebeat - your point about the drylining being on the blocks is one of the points i was concerned about. i am taking it from your answer that it is not standard practice for the builder to put a scratch plaster layer under the drylining?

if i get him to do this would this substantially improve the air tightness?

i intend to get the air tightness test done after first fix is completed to fix any major issues before the final plaster finish on the wals

What result are you aiming for?

Google 'Enhanced accredited details' - recommend scratch (Parge coat) on walls.

Did you know the AVERAGE permeability of standard constuction WITHOUT any tape - infact any knowledge of permeability - is around 5 @Q50 in SW region. No tapes/No special training/no mid construction testing? How do they do it? Building Control inspection perhaps???

Ps 5 might not be that excellent - but what level do you want get to?

fitzie79

hi ardara1 - i have heard figures of approx 3 air changes being recommended for hrv installation but a maximum of 5 in order for the system to be useful. i would be aiming for around 3 hoping that the mid-construction air tightness test and good taping would help me achieve this. is this realistic? i won't have an open fire, will use a recirculating extraction fan and wont have any trickle vents in the windows if i go with this system