external walls what type insulation

Viking House

Hi Adara

What did you tape the joints with to get Vapour Control?
Aluminium foil tape - expensive - but sticks like s*** to a shovel!

Plasterboard being vapour open allows moisture through, so moisture is probably getting into the plasterboard, migrating towards the edges behind the foil tape through the gap between the insulated plasterboard and condensing on the wall. You won't see this unless you rip it off the wall.

Would Polyeurethene foam have worked better between sheets?

Viking House

The reason the foil is on the insulation is to try and stop the blowing agents from migrating/escaping. Its actually used for improve emission of heat from the board, if it was for gas sealing then aluminium wouldn't need to be used and a vapour proof polymer could be used instead
Polysterene uses a similar blowing agent and they let is escape but Polyeurethene tries to hold on to it giving it a better U-value initially, the foil is used for 2 jobs, to reflect back radiant heat and to stop the gas escaping.


U-value alone is not enough when you are calculating heatloss through a wall, the density/weight of the insulation is also a very important factor.
But the density/weight of the whole wall, blocks insulation and finishes, should be taken into account. Not just the insulation. When dealing with a block wall the density of the insulation makes little difference to the density of the overall wall.
I don't rate concrete blocks when it comes to Thermal Mass because they are always cold and damp even when I brought one into my living room for a week. When they are dry they let out their heat in 3 hours, when they are damp it is a lot quicker.
I recently read a German article that showed when you put non breathable insulation onto a block wall only 80% of the U-value of the insulation is realised because the wall was prevented from drying out and stayed damp reducing the overall U-value. Concrete is refered to as a cold building material in Scandinavia and they try to reduce the amount as much as possible for that reason.
To have a decent effect on Thermal Mass a block has to have a reasonable U-value.


I agree with what you are saying, some of it takes my comments out of context. I did not mean to do that as I have always respected your opinion.
I believe the more we debate these items the greater our knowledge will become.

Mellor

Viking House wrote:

I believe the more we debate these items the greater our knowledge will become.

Absolulely. 100% agree.

The amount of heat that concrete holds isn't that high. Timber is far higher, BUT this is measured per KG. So even though timber holds more heat per KG, because concrete is far more dense it holds on to more heat per volume.

Take clay dome house with very thick in the desert as an example. The reason they work so well is that the walls are so dense, they dont hold on to much heat per KG but this is outweighted by the density, this walls are very similar to concrete.

Large scale buildings that have an advanced thermal mass system use concrete as the thermal material. Either to store and distribute heat, or inversely to remove heat. Where concrete slabs are cooled during summer nights which creates an imbalance in the room that has to be overcome before the room heats, this system is used to prevent overheating days in buildings (if they're are more than 5 overheating days then a mechanical cooling system is need, this comsumes alot of energy)

U-Values are not the final say in any building. In domestic buildings they matter far more than in larger buildings. In a house, if you lower the u-value the energy will drop. other things matter too, and changing construction and keeping low u-values can also cause energy to drop. but lower u-values will always cause energy to drop (at current achievable standards)
But in large buildings, lower u-values can actually increase energy use, this isn't always the case and is normally in low energy buidings. I only included this for reference and it doesn't apply to houses, the internet can be dangerous and i dont want people to take that information up the wrong way.

Viking House

ardara1 wrote:

What did you tape the joints with to get Vapour Control?
Aluminium foil tape - expensive - but sticks like s*** to a shovel!

Did you also tape where the plasterboard meets the floor and ceiling?
Mastic sealant top & bottom.

How did you deal with the moisture that got through the plasterboard ceiling of the kitchen and migrated towards the external wall?
The kitchen was a reasonably recent extension (2000) no problem anywhere yet.

Hi Adara

How did you deal with the fact that the timber joists were the only escape route for moisture to travel towards the external wall. If everything else was sealed up this would be the only route for moisture to travel. When the moisture entering the joists is greater than the moisture escaping due to Hydroscopicity then moisture will build up in the wood leading to rot when the levels reach 18%.

Moisture can also get into the plasterboard, behind the tape, through the gap between the sheets leading to condensation on the walls behind the insulated plasterboards.

bcoffey

Hi all,

anyone heard of anyone that has used Finlay Breton's 'Finlite' blocks,
which are a lightweight block and claim 300% improvement on
insulation over standard blocks (with no obvious disadvantages)?

http://www.jfinlay.co.uk/blocks.htm

ardara1

bcoffey wrote:

Hi all,

anyone heard of anyone that has used Finlay Breton's 'Finlite' blocks,
which are a lightweight block and claim 300% improvement on
insulation over standard blocks (with no obvious disadvantages)?

http://www.jfinlay.co.uk/blocks.htm

Hi BC - had a look at them - 0.33 of a K value - so pretty good thermally but the beauty is in the loading - it's a 7N strength so perfrect for bring walls up and reducing the thermal bridging at wall floor junctions

Viking House

ollie30 wrote:

how about 150mm cavity with 140mm aerobord platinum to get u value down to either .19 or .20 depending if your using brick or double leaf block,they even supply the ties in the price and a lot cheaper than the 100mm kingspan in 140mm cavity to get same values.its about 4 or 5 euro sqmtr cheaper and kingspan ties are extra.call aerobord in co.cavan for info i found them very helpful

I spoke to a guy from Aerobord who has just qualified as an energy assesor.
He said that you have to add 0.11 to the U-value of the wall to allow for the cold bridge between the walls and the floor when you use a partial fill cavity wall construction.
So a U-value of 0.2 becomes a U-value of .31 when you add in the cold bridging effect.
This figure does not allow for the cold bridging around the windows and doors which could add another 0.11 to the figure giving you U-value of 0.42 for the walls.

Comments welcome please because I think this is a major issue and I would welcome some debate on it.

Viking House

ardara1 wrote:

Hi BC - had a look at them - 0.33 of a K value - so pretty good thermally but the beauty is in the loading - it's a 7N strength so perfrect for bring walls up and reducing the thermal bridging at wall floor junctions

They look to have the same U-value as about 10mm of Polysterene.

Noviceman

hey, dragging up this thread again,

Viking House, you mentioned about using Polyeurethene foam to seal the insulated slabs/ Would you recommend sealing all the joint, ie between slabs, floor to slab, slab to ceiling.

was just looking at this site http://www.spray-insulation.co.uk/index.htm, has anyone ever done this diy, would they recommend it... for the insulated slabs anyway, not so sure about other parts of house

Viking House

Noviceman wrote:

Viking House, you mentioned about using Polyeurethene foam to seal the insulated slabs/ Would you recommend sealing all the joint, ie between slabs, floor to slab, slab to ceiling.

was just looking at this site http://www.spray-insulation.co.uk/index.htm, has anyone ever done this diy, would they recommend it... for the insulated slabs anyway, not so sure about other parts of house

If I was doing it I would seal up all the joints but you are still faced with the problem of moisture making its way through jhe timber joists as it is the only hydroscopic route left open, leading to the risk of rot.

Moisture from your house is probably sweating over the complete surface area of a wall, by using that type of insulation you are concentrating the moisture to the only exit available which is the wood in the studs leading to the same problem as above.