filling the cavity in TF homes

KAGY

Hi,
I'm looking into the possiblity of increasing the U-value of the wall in my house by retro-filling the 50mm gap between the timber frame and the external block work with something.
Has anyone any thoughts about this, and do you think that there would be a problem with moisture ingress / bridging?

yop

I don't know for certain Kagy but I would say that would be strong advised against as you would be stopping air circulation

Viking House

We leave out the external block altogether and put a 4inch layer of granitewool insulation on the outside of the timber frame and plaster directly onto that. We also put 2 inches more insulation on the inside of the frames at right angles to the stud cutting out cold bridgeing through the wood.
This gives a U- value of 0.14 and eliminates the need for a heating system.

KAGY

Viking House wrote:

We leave out the external block altogether and put a 4inch layer of granitewool insulation on the outside of the timber frame and plaster directly onto that.

I would have loved to have done that, but the house is 2 year built and I only discovered that method recently, so I'm looking for a retrofit method. That's why I thought of foam injection. I think it would also seal the house solving some poor builder issues.

YOP: I don't think that the air circulation would be a problem if I could be assured that no water was getting past this new insulation to the timber frame.

ardara1

Why are you finding it necessary to pump the cavity in Timber Frame - Is it colder than you thought? - What insulation was placed between the studs originally? What depth were the studs?

Canadian systems normally put inslation into the conventional cavity - but always partial fill - normally extruded EPS.

If you've brick facings anywhere on the building, you'll not be allowed to use full fill any way.

Viking House

I would be concerned about your house sweating if you filled the cavity with foam. Shredded Rockwool or Cellulose would be my choice. Use a Drywit or Stoe type fibreglass mesh supported mineral plaster on the outside which is resistant to cracking and moisture penetration but is breathable.

What stage is your house at? It is important to put a very good quality vapour control layer internally to avoid moisture getting into the frames from the inside.

Cmar-Ireland

Viking House wrote:

We leave out the external block altogether and put a 4inch layer of granitewool insulation on the outside of the timber frame and plaster directly onto that. We also put 2 inches more insulation on the inside of the frames at right angles to the stud cutting out cold bridgeing through the wood.
This gives a U- value of 0.14 and eliminates the need for a heating system.

This sounds very interesting.
Couple of questions...
Is the granitewool a strong material? I mean, if you knock against an external brick finish, it would take a lot to damage it. Would the plaster crack easier if knocked?

How does the low U-value eliminate heating requirments. Would you not need something, however small, to provide space heating?

How do you fix the internal slabs over the extra insulation?

Cheers

KAGY

No the house isn't very cold, but now that's it's built and the initial expense is over I'm turning my thoughts to increasing the insulation.
As I said in a previous post, there are some residual bad build(er) issues, some of the plugs have a draft coming in them, which suggests to me that some of the cavity barriers are missing and / or that there is a hole in the frame somewhere.
[size=-2] if anyone is building in the Westmeath / Longford border area PM me and I'll give you the name of the builder[/size]

Because of this and other issues I am now not confident that the builder took the greatest care in putting the 150mm Fibreglass into the studs. In fact in one or two places (but not all) where the plasterboard had broken at the ground level there was a gap in the insulation of an inch or two.

So I was thinking that I have a cavity that I could maybe fill with a continous insulant to seal up the house and bring the house a bit closer to passive, without having to redecorate the inside.
My calculations suggest that it would bring the current U value of the wall from 0.27 down to 0.2 W/m2K possibly saving 10% of my heating bill (currently over €1200; a GSHP)

However, if there is going to be a problem with damp getting in or condensation (is that what you mean by sweating viking house?) I'll probably leave it and look at other energy saving methods.
Now there's an interesting thread on building your own turbine over on green issues......

Viking House

Is the granitewool a strong material? I mean, if you knock against an external brick finish, it would take a lot to damage it. Would the plaster crack easier if knocked? Its quite resistant and is similar to the front bumper of a car, it will resist a 10mph bang from a car but not a teenager with a penknife, but you can also put steel mesh into the plaster to make it penknife resistant.
How does the low U-value eliminate heating requirments. Would you not need something, however small, to provide space heating?

How do you fix the internal slabs over the extra insulation? You just cross batten internally with 2 x 2 wood and run the insulation between the battens.

Hi there Cmar

I spoke to client yesterday living in a Passive house.
He is a farmer and works outside all day and his wife has a day job so there is nobody at home all day.
He has turned on his 3 bar electric heater for half an hour 3 times this year so far because his house was chilly.
He has not followed all of our guidelines and has no insulation between floors and has not cocooned his living area off from the rest of the house with insulation. He has only one door connecting the living area to the outside when it would be better to have two doors and a porch to avoid heatloss.

Cmar-Ireland

Could you use the external layer of granitewool and still build a brick/block wall to provide a more solid external finish while retaining the insulation properties?
Forgive the questions, but are you saying this guy heats the house with a 3-bar?

In a situation where a new TF house was being built. If the external walls had the 4"+2" and external granitewool and internal walls had 4" insulation. Between floors has 4" and attic 12". The heating requirments would be very low?

Viking House

Hi Kagy

KAGY wrote:

Some of the plugs have a draft coming in them, which suggests to me that some of the cavity barriers are missing and / or that there is a hole in the frame somewhere.
In fact in one or two places (but not all) where the plasterboard had broken at the ground level there was a gap in the insulation of an inch or two.
So I was thinking that I have a cavity that I could maybe fill with a continous insulant to seal up the house and bring the house a bit closer to passive, without having to redecorate the inside.
However, if there is going to be a problem with damp getting in or condensation (is that what you mean by sweating viking house?)

Because the vapour control membrane is damaged or missing, the biggest risk to your TF house is from moisture coming from inside your house causing damage to the timber frame and moisture getting into the insulation, reducing its performance. If you pumped the cavity with non breathable polyeurethene without addressing the Vapour control problem you could exaggerate this problem.

Viking House

Could you use the external layer of granitewool and still build a brick/block wall to provide a more solid external finish while retaining the insulation properties? There is no need for a more solid external finish, because it is really strong but you can glue brick or stone slips onto the granitewool if you want.
Forgive the questions, but are you saying this guy heats the house with a 3-bar? Yes for the moment, but he is waiting to get a mini wood chip boiler back up system

ardara1

Because of this and other issues I am now not confident that the builder took the greatest care in putting the 150mm Fibreglass into the studs. I

My calculations suggest that it would bring the current U value of the wall from 0.27 down to 0.2 W/m2K possibly saving 10% of my heating bill (currently over €1200; a GSHP)

issues......[/QUOTE]


Hi Kagy - Here's part of you prblem - you're not any where near 0.27 to start with.

Your timber studs are 140mm - your fibreglass I presume is standards fibre with a conductivity of 0.044 - your ACTUAL U-value is 0.32 - not 0.27
Check out the UKTFMA web site for their document on reaching Part L - it's veridied in that document - also in our own Part L document.

You'd need 140mm Aerobord insulation in 140mm stud to get to the 0.27 elemental value (Elementally your house doesn't meet the building regs) - get back to your Timber Frame supplier.

KAGY

ardara1 wrote:

Hi Kagy - Here's part of you prblem - you're not any where near 0.27 to start with.

Values I used are as below, calculated using an SEI spreadsheet to give 0.27. The cavity and the block are having some effect. I know that in reality air circulation negates this bringing the cold air from outside into the cavity, but it is ignored in the building regs (albeit wrongly so). Traditional building quality can reduce the design U value by at least half, as was demonstrated by BRE in the UK I think.



External surface resistance 0.06 W/m2 K
1 Block 115mm 0.51W/m K
2 Cavity 50mm 0.18W/m2 K
3 OSB 12mm 0.14[W/m K]
4 Stud work / fibreglass 140mm 0.04 [W/m K]
bridged by Timber 0.14[W/m K] 10% bridging
5 Plasterboard 12mm 0.16[W/m K]
Internal surface resistance 0.12 W/m2 K

KAGY

A back of envelope cost-benifit, together with your responses, has put me off this. With my calcs, its a 25 year payback. Although if what ardara1 is saying is true, I've underestimated the benifit

ardara1

KAGY wrote:

Values I used are as below, calculated using an SEI spreadsheet to give 0.27. The cavity and the block are having some effect. I know that in reality air circulation negates this bringing the cold air from outside into the cavity, but it is ignored in the building regs (albeit wrongly so). Traditional building quality can reduce the design U value by at least half, as was demonstrated by BRE in the UK I think.



External surface resistance 0.06 W/m2 K
1 Block 115mm 0.51W/m K
2 Cavity 50mm 0.18W/m2 K
3 OSB 12mm 0.14[W/m K]
4 Stud work / fibreglass 140mm 0.04 [W/m K]
bridged by Timber 0.14[W/m K] 10% bridging
5 Plasterboard 12mm 0.16[W/m K]
Internal surface resistance 0.12 W/m2 K

1. Block used at 0.51 is foro MED density block - not available in Ireland - you used dense blocks at 1.15

4 Fibre glass std has a lambda of 0.44 not 0.40 unless you bought a HD material? (Bt I doubt it - it's V Expensive)

4 THE BIGGY - 10% BRIDGING? BR443 (THE STD BY WHICH U-VLAUES MUST BE MEASURED STATE THAT THERMAL BRIDGING FACTOR MUST BE TAKEN AS 15% MINIMUM IT'S PROBABLY MORE THAN THIS AS THE 15% IS BASED ON STUDS AT 600MM CENTRES. OUR PART L STATES THAT IF THERMAL BRIDGING IS OVER 16% IS MUST BE QUANTIFIED AND USED IN THE CALC - USUALLY IGNORED.

Int resistance should be 0.13 and external 0.04 but these (including the block value are minor considerations it's the thermal bridging that puts your figure out.

KAGY

Thanks for that, but I'm still under the elemental rating according to teh 2002 regs (0.37). I'm sure that there are still several heat bridges that would increase the heat loss figure.
Which brings me back to the origin of this post. I there anything that I can do retrospectively that would insulate the walls better, without major internal decoration? It appears that foam is out from this discussion

BTW. I know it's a typo, but the lambda of fibre glass is 0.044

ardara1

KAGY wrote:

Thanks for that, but I'm still under the elemental rating according to teh 2002 regs (0.37). I'm sure that there are still several heat bridges that would increase the heat loss figure.
Which brings me back to the origin of this post. I there anything that I can do retrospectively that would insulate the walls better, without major internal decoration? It appears that foam is out from this discussion

BTW. I know it's a typo, but the lambda of fibre glass is 0.044

Technically the 0.37 figure is accepted as worst case under the Overall Heatloss Method in 2002 regs - however - what were you told you were going to achieve - that's the point, most people putting up timber frame believe that the performance is better than traditional build, having a perception that TF is super efficient.

I think that upgrading the walls at this stage would be uneconomical - try improving energy efficiency somewhere else - Heating Control? Boiler Efficiency - more insulation in the loft? - you can compensate for the short fall in the walls by other efficeincies.

galwaytt

Because of that very issue you describe - incomplete or possibly incomplete filling of the stud, my new house - currently being finished -has the stud pumped with cellulose fibres...........nice and dense. Excellent.

However, I then changed job to a new company manufacturing SIP's - Structural Insulated Panels - and one of the huge benefits is the integrity of the panel (air tightness). In the process of getting Agrement approval for the houses, we looked at a whole bunch of cladding alternatives. One thing you could do, reasonably easily - but still not for the light hearted - is to dry line the house with Warmboard. This is a urethane-backed plasterboard, and can have a huge impact on your u-values.

You only need to do the ext walls, remember, not partitions, but if your house is 100% finished, you'll have to undo some of that........eek !

renedescartes

Hi Kragy,
If you want to improve your heat loss try putting aluminium foil in your attic space. There is a product called SuperR foil. It can be done DIY. It reduces radient loss and reduces gain in summer. It works!
Michael