warmcosy
Unregistered User
New house insulation
I am about to start building a new house and am trying to decide the best method for insulation.
I was going to use traditional cavity wall insulation (Kingspan 50MM) but several people have said to forget about this and use insulated plasterboard on the inner surface of all external walls in the house. I imagine that this would be fairly expensive for a 3200 sq foot house.
Also is it the best method for a house that will be heated by underfloor heating??
Would insulating the walls from the heat prevent them from acting as a heat store for the house??
I had a look at the thread on insulation for info on this but I didn't really get an answer!
Any help appreciated!
legend99
Not an answer to your question...but a further question. How much is a 3200 square foot house working out at in terms of building costs??
Incidentally, my understanding was that the evolution of walls has been:
Solid walls as thick as you could make them
Then cavity block walls
Then two side by side walls with an air gap in between
Then came two side by side walls with aeroboard between them
And since then it has been the aeroboard that is getting thicker.
So not sure what might be better. But we had to dry line our old house with those foam backed platser boards...you can get 1/2, 3/4 and 1 inch foam backing I think. But you're right, it puts a serious cost onto the plaster board. To be honest, I thought if you have the two side by side walls with the 50mm or whatever it is of aeroboard that you really wouldn't need more foam on the back of the plaster board...but I'm no builder!
Laoise
Unregistered User
internal insulation
Not a good idea.
It's hard not to get cold bridges where the internal walls meet the external wall.
Imagine two rooms side by side along the external wall. You insulate all around each of them on the inside. The dividing wall between the rooms is touching the cold external wall. There's no insulation outside the external wall - so the dividing wall is cold where it meets the external wall. Precisely there where the interior insulation has a corner join ..........
Not a good idea.
warmcosy
Unregistered User
Still having a cavity..
Thanks for the comments so far!
legend99, I am budgeting for around €240,000 building by direct labour and I just hope that's enough. All the same I still don't want to skimp on the insulation.
Laoise, I may not have made it clear enough in my initial question but I still intend having a cavity wall but I just wouldn't put any insulation in it- I would use the insulated plasterboard instead on the inner surface of all external walls.
Laoise
Unregistered User
insulation
OK, makes it slightly better - but you'll still get some cold-bridge effect. Anyway, seems a shame to build a cavity and not fill it.
In principle, insulation is always more effective on the outside of the house.
Generally, internal should only be used when other influences are in play - such as retro-insulating an old building where you can't change the facade to allow outside insulation etc.
While on the topic, don't forget to insulate under the floor - rarely done in Irish houses, but of enormous effect, especially if your'e installing under-floor heating.
John
Unregistered User
cavity block wall
What exactly is a cavity block wall ? We have an old house with such walls (built 1960s). They said he have a cavity block wall and a honeycomb centre and an external leaf ?? We were trying to get pollypearl inserted but we cant. I dont understand it.
heinbloed
Unregistered User
insulation
Why going for cavity walls in the first place?Ask your engineer about the "dew point" and the reason why he thinks that there should be an outer leaf of blocks.It makes no sense except feeding some builders pocket .If the outer leaf of blocks is insulated by polyurethane from the inner wall it gives a calculate able better U-value,but just in calculations.For real comfort and energy saving it makes more sense to put the heat storage capacity(the solid wall) on the inside of the building and the insulation on the outside.Does a polar bear wear a second layer of flesh and bones on the outside?
Kingspan PU-boards are expensive ,go for expanded polystyrene boards,glued on the outer wall and plastered.
That is if you can't find a builder who can build a wall without concrete.Concrete is a bad insulator.
So if you have the choice don't waste the money on something that does not pay back.
Timber frame is better insulating than concrete.Poroton is something between timber frame and cavity wall.It allowes for moisture exchange(provided it is not sealed with cement plaster) and gives perfect insulation,far beyond building regs.And it has thermal mass and some sound insulation qualitys.All in one wall,without the need for extra artificial insulation.And due to it's fast erection time-and no drying time-it is cheaper than a cavity wall.
LIDL supermarkets here in Ireland are now being build with these blocks.They are able to calculate with a sharp pen if you know what I mean.
Check
www.fbt.ie
I have no connections to the company except that I used these blocks for my own home and never regretted it.
And for your underfloor heating:a minimum of 55mm insulation is recommended by manufacturers,my advice is at least 110mm,manufacturers have a tendency to play down the costs if it is not their material -the insulation-that the costumer is spending money on.On the continent they have the same soil temperature as here,but 55mm insulation under a house is against the building regs..
legend99
Posts: 395
Hein,
I thought most builders in Ireland doing domestic house would go for the outer wall of solid block, with the aeroboard in the middle on those metal tie things and then an inner wall of solid block with the plaster board just on the inside of that inner wall?
Is that a crap way to build?....most domestic dwellings I have seen during the build are done like that no?
heinbloed
Unregistered User
cavity walls
They are.These building methods where developed as standard when builders went abroad to find a job,when man hours where cheap and heating material-fuel-was cheap ,providing jobs in the bogs.The times have changed but builders are slow to change.I remember 20 years ago people did not believe that timber frame "works",the whole of the industry lamenting.20% of the buildings nowadays are build by this technic.In the beginning crews from the US and Canada and other countries where flown in to build a few timber frames.The same story with log homes 10 years ago.Actually the Lidl supermarket chain gets gangs from Germany flown in because the Germans are used to the poroton blocks,not because it is difficult to work with the material or because there is some trick.
Builders in Ireland don't have the theoretical background to change easily to new methods.On the continent an apprentice bricklayer learns for 3 years incl.schooling and if he wants to run his own company he needs a master degree.Another 2 years incl.school.This theoretical knowledge enables him-and more and more also HER-to do the necessary calculations like load bearing capacity and k-value etc..Ask an Irish bricky a question like what is the U-value of a wall or the wind stability.They do what they are used to ,hardly learning new things job wise during their lifetime.
I talked to a retired driver from Murphys Brewery.He worked there all his life,more than 40 years.And he told me that beer was made from hops as the main ingredient.Hops is the smallest amount of beer ingredients,the preservative.I did not want to insult the poor man and said nothing.But it shows how interested people are and how difficult it is for people to learn once they feel safe (by having a job).Especially when they are paid per laid block,plus per square foot of aeroboard and for every wire tie extra.If this job can be done with just one block ,well .....and than they are supported with " facts" and stories by the concrete and aeroboard industry,both been fined by the EU competition commissioner for defrauding the costumers.
And Mary Harney is asking us for suggestions......