Insulation

newbuild06

Morning all

My cousin is starting on the long road of building his own house. He is thinking of going with a 2 story house (if the planners allow). He is pretty certain that he wants to go down the road of block build.

I mentioned to him that he could now get external insulation on his house and he seemed interested in this?

Has anyone on here used external insulation and if so how good do you find it?
What sort of u values does it offer ?

How does the block construction work with external insulation? Do you need to do anything differently?

Sorry for all the questions on a monday morning

sas

newbuild06 wrote: »

Morning all

My cousin is starting on the long road of building his own house. He is thinking of going with a 2 story house (if the planners allow). He is pretty certain that he wants to go down the road of block build.

I mentioned to him that he could now get external insulation on his house and he seemed interested in this?

Has anyone on here used external insulation and if so how good do you find it?
What sort of u values does it offer ?

How does the block construction work with external insulation? Do you need to do anything differently?

Sorry for all the questions on a monday morning

Don't have it but if money stretches that far I would really like to use it.

It can offer pretty much any u-value but in all practicality it tops out around 0.1 This will mean approx 315mm of EPS insulation.

Instead of 2 leafs of block work you have a single leaf with blocks on the flat i.e. 215mm solid wall with no cavity.

Don't underestimate how expensive it is...

newbuild06

sas wrote: »

Don't have it but if money stretches that far I would really like to use it.

It can offer pretty much any u-value but in all practicality it tops out around 0.1 This will mean approx 315mm of EPS insulation.

Instead of 2 leafs of block work you have a single leaf with blocks on the flat i.e. 215mm solid wall with no cavity.

Don't underestimate how expensive it is...

If i can remember righlty we got a quote for it when we were building but i think at the time there was only one company out there doing it and we could find no people with experience of it. i think our quote for a 2,500 sq ft house was around 18,000 and i dont know if this included rendering or not. i will have to look it up. It seems like a really good idea but if this is the price i dont know how cost efective it is.

The only other real option for him if he goes with the blocks then is insulation in the cavity and insulated plasterboards ?? or is there something else out there

conor2949

Hi there,

For my 2 cents worth, I plan building a 2950sq ft dormer bungalow (velux's in roof not dormer windows).

My quote for 120mm external insulation finished in acrylic plaster of any colour i like is 23k plus 13.5% vat thats fully installed and finished by them. Or i could get it in a DIY kit for 16k.

The U value for this is 0.23 if i remember correctly.

I am going to go with it. I've done a bit of research and I think it gives a more robust solution to the insulation issues out there. By this I mean that the insulation in a partial fill cavity needs to be exactly flush with the internal wall otherwise it doesn't perform as effeciently and other issues such as windchill if the cavity isn't sealed up properly.

However I am not building a block on the flat - I am going with a 310mm cavity (block - 110mm cavity - block). I am going to pump bonded bead into the cavity to fill it up completely. Yes it might seem like overkill but if i go with 6 inch block on the flat then I have issues with needing deeper window cills, accomodating services (because i'm not drylining), etc.

again just my two cents worth.

Conor2949

sas

conor2949 wrote: »

However I am not building a block on the flat - I am going with a 310mm cavity (block - 110mm cavity - block). I am going to pump bonded bead into the cavity to fill it up completely. Yes it might seem like overkill but if i go with 6 inch block on the flat then I have issues with needing deeper window cills, accomodating services (because i'm not drylining), etc.

Conor2949

You're quote info. would be more useful if you told us how many square metres you were priced for.

You have me very confused. Can you explain why you believe block on the flat presents issues for your cills that your suggestion gets around?

Plus I don't see how it solves your service issue either. The vast majority of services in regular houses are chased into the inner leaf of block work anyway.

RKQ

Why increase the cavity to fill it with bead?

Why not have a 40mm clear cavity and spend the money for bead on extra thick exterior wall insulation?

SAS is right, I'm surprised by your claims regarding deeper cills and services. A block laid flat or instally vertically won't effect either cill depth or service chase.

The exterior insulation thickness will effect cill depth!

Slig

There is so much enphasis on getting as much insulation as possible into walls now that I dont think people are considering all the implications.

You cant always just mismatch different insulations, they all have their seperate properties. I personally believe that Polystyrene is the only insulation material that should be used in damp environments, Polyurethane should be used in dry environments and Mineral/glass fibre where breathability is essential.

I can see problems where these materials are not used in the correct locations, like PU board in cavities (I know I'll get flak for this but..) PU desintegrates in moisture rich environments.

I would be more in favour of a full fill Aeroboard T&G cavity board in an external cavity wall then the more high performance PU board.

I also dont see the point in putting an external insulation on a cavity wall, the heat leaving your house meets a drafty air cavity before it hits the insulation

sas

Slig wrote: »

I also dont see the point in putting an external render on a cavity wall, the heat leaving your house meets a drafty air cavity before it hits the insulation

I'm assuming you mean an "external insulation on a cavity wall". I thought this a little strange my self.

My understanding is that the inner surface will be your airtightness layer. If you introduce a cavity you won't be able to plaster the inner surface of the outer leaf to create the air tight layer. Even if you could you are now left with a ventilated cavity that you will also have to try and make airtight which would be great fun around the wall plate I'd imagine.

conor2949

the quote was for 254m2 (or so they detailed on the quotation - all i can do in cad is pan and zoom)

My concern with a 40mm cavity is that there would be a wind chill if not sealed properly.

if i build a block on the flat will there not be a bit of an issue with incorporating an ESB meter box into the wall? will it not require significant cutting into the block to allow it to sit flush with the exterior?

I intend using polysytrene for both external and full-fill insulation.

Point accepted on the deeper cills - you just refreshed my memory. I wanted to go with deeper external insulation but that meant deeper cills hence i thought i would be smart and just fill the cavity. thus no deeper cills required, no departure from conventional build approaches and it was cheaper to fill the cavity with 100mm bead than add it onto the outside.

sas

conor2949 wrote: »

the quote was for 254m2 (or so they detailed on the quotation - all i can do in cad is pan and zoom)

My concern with a 40mm cavity is that there would be a wind chill if not sealed properly.

if i build a block on the flat will there not be a bit of an issue with incorporating an ESB meter box into the wall? will it not require significant cutting into the block to allow it to sit flush with the exterior?

I intend using polysytrene for both external and full-fill insulation.

Point accepted on the deeper cills - you just refreshed my memory. I wanted to go with deeper external insulation but that meant deeper cills hence i thought i would be smart and just fill the cavity. thus no deeper cills required, no departure from conventional build approaches and it was cheaper to fill the cavity with 100mm bead than add it onto the outside.

254 metres squared for that price sounds very good to me. Most of the price on EWI for what I've seen is for labour and the render. So increasing the outerleaf shouldn't cost too much. Would you PM me the supplier please.

The ESB box is a good point. I'm hoping to convince the ESB to break their rules about the positioning and put it on the garage. That's assuming I got for EWI of course.

Incidently, this is the best detail for fitting windows on an externally insulated house according to the PHI. window_installation.jpg
You simply externally insulate the wall and around the window.

conor2949

PM sent sas

yeah i thought it was a good enough price too. a little over 102 euro per sq metre including the dreaded VAT.

I tried explaining there was no VAT in tipperary but he didn't seem to hear me.

you'd have to do a very merry dance to get them to do that. even if they did wouldn't you have to use Steel Wire Armoured cable in ducting over to your fuseboard? that could cost a small fortune depending on where your garage is relative to house.

Slig

sas wrote: »

254 metres squared for that price sounds very good to me. Most of the price on EWI for what I've seen is for labour and the render. So increasing the outerleaf shouldn't cost too much. Would you PM me the supplier please.

The ESB box is a good point. I'm hoping to convince the ESB to break their rules about the positioning and put it on the garage. That's assuming I got for EWI of course.

Incidently, this is the best detail for fitting windows on an externally insulated house according to the PHI. window_installation.jpg
You simply externally insulate the wall and around the window.

You could then use a profiled metal/aluminium cill instead of a concrete one

sas

Slig wrote:

You could then use a profiled metal/aluminium cill instead of a concrete one

That's the plan. Although I've seen one house done where they created the cill out of the EPS as they went.

sas

conor2949 wrote: »

you'd have to do a very merry dance to get them to do that. even if they did wouldn't you have to use Steel Wire Armoured cable in ducting over to your fuseboard? that could cost a small fortune depending on where your garage is relative to house.

Merry dance possibly. But a fellow I grew up with works for the ESB and may be wiring my house. He didn't seem to think it would be that big a deal. Access to the meters should be less of a big deal given that smart metering is somewhere in the pipeline...

No idea to be honest on the ducted cabling. Does anyone know if its acceptable to surface mount the box in some sort of enclosure? I've seen some of the closed panel timber frame conpanies do this. It's very unsightly so I would stick it down the side of the house where it's out of the way.