EWI or pumped beads or both

soccercrew

Im looking into EWI or pumped insulation for my dormer bungalow. Ive gotten a quote for pumping beads at 800ish and the materials for the ewi are coming in at 2400euro and if i remember correctly, thats with 100mm ewi insulation. Ill be putting the ewi on myself with the help of another plasterer so wont be spending huge amounts of money on labor.

What i want to know, would reducing the ewi thickness and pumping the walls with beads be more efficent than having 50mm aero board,50mm cavity then block and 100mm of ewi. Ill also be upgrading my internal insulation in my voids in dormer with 150mm-200mm of knaff or other material.

air

soccercrew wrote: »

Im looking into EWI or pumped insulation for my dormer bungalow. Ive gotten a quote for pumping beads at 800ish and the materials for the ewi are coming in at 2400euro and if i remember correctly, thats with 100mm ewi insulation. Ill be putting the ewi on myself with the help of another plasterer so wont be spending huge amounts of money on labor.

What i want to know, would reducing the ewi thickness and pumping the walls with beads be more efficent than having 50mm aero board,50mm cavity then block and 100mm of ewi. Ill also be upgrading my internal insulation in my voids in dormer with 150mm-200mm of knaff or other material.

You'll need to pump anyway if doing the EWI, otherwise air circulation in the cavity will mean the heat escapes before it reaches the EWI.

soccercrew

air wrote: »

You'll need to pump anyway if doing the EWI, otherwise air circulation in the cavity will mean the heat escapes before it reaches the EWI.

Are you sure about this. Would closing of the top with more insulation not create an air gap like in double glazed windows and not benefit it more. Probably wishful thinking on my behalf and its well out of what i know but its something that crossed my mind. If i do have to pump, ill probably be best to reduce the ewi to 50mm then and this should have the same benefits of a solid wall with 100mm ewi

chillit

a large part of the cost of EWI is the labour. Also the renders are quite expensive. Increasing or decreasing the thickness of the insulation shouldn't have a huge bearing on the price so go for as thick as you can.

I would stick with the 100mm if I were you. 160mm or 200mm is even more recommended but probably only of value if you are considering other factors such as airtightness at the same time.

air

Definitely wishful thinking, the cavity won't be next or near the level of air tightness required for the air gap to contribute to the insulation.
Double glazing is perfectly sealed & even then it's filled with argon or similar nowadays to further improve the u value.
Chillit is spot on also.

soccercrew

chillit wrote: »

a large part of the cost of EWI is the labour. Also the renders are quite expensive. Increasing or decreasing the thickness of the insulation shouldn't have a huge bearing on the price so go for as thick as you can.

I would stick with the 100mm if I were you. 160mm or 200mm is even more recommended but probably only of value if you are considering other factors such as airtightness at the same time.

Ill be able to save on labor with doing it all myself. Huge expense saved if i go down this route. I can only go 100mm max because of my soffit board on both gables. Maybe stretch it 150mm back and front but couldnt get away with it at sides. Ill be insulating this house now while i have the money before oil prices rise again in future and will be looking into sealing any air leaks aswell.

MicktheMan

Is this a newbuild or retrofit?

soccercrew

MicktheMan wrote: »

Is this a newbuild or retrofit?

Retrofit. House built 18 years ago with terrible building insulation regs. House heats up ok but loses it very quickly.

MicktheMan

soccercrew wrote: »

Im looking into EWI or pumped insulation for my dormer bungalow.

soccercrew wrote: »

Retrofit. House built 18 years ago with terrible building insulation regs. House heats up ok but loses it very quickly.

Odds are you have an airtightness issue which adding / upgrading wall insulation will do nothing for.

Dormers are notorious for this.

Get the house tested for air tightness to understand what is going on.

yupya1

Best bet is foam pumped into the cavity, much better than Beads and will solve the air tightness.
With the foam you won't need the cumbersome ewi either.

I've recommended these guys before who did my house. Great job www.shannoninsulations.com

MicktheMan

yupya1 wrote: »

Best bet is foam pumped into the cavity, much better than Beads and will solve the air tightness.

It won't. Not in a dormer.