Insulation comparison

fitzie79

I have recently gone to tender to build my bungalow. Got the first quote back today and it is around what we would have expected. However, instead of quoting for what we specified in the tender document they have quoted for their own recommended insulation.

In the tender document we specified the following:

External twin leaf cavity walls to have 60mm rigid Kingspan Hytherm insualtion.
50mm insulated gyproc plaster slabs to internal faces of all external walls

However, they quoted for full fill bead insulation in the cavity. Additionally, they said that they would insulate all underfloor radiator pipework and provide 300mm cellulose pumped insulation to the attic space.

My impression from what I have read is that there are issues with moisture ingressing across the cavity with the pumped bead insulation and that it degrades over time. Would their proposed solution provide inferior performance in both the short and long term?

RKQ

Not meaning to be blunt, but whose house is it?

If I ordered a meal in a restaurant I'd be more than a little upset if the waiter came back with a meal he thought I'd prefer!

Why can't they price the specification / drawings supplied?
How can you compare prices if everyone is doing their own thing?
Who is Certifying / inspecting the construction? - How will they feel about these proposed changes?

I'm not commenting on the insulation that they are specifying / changing, just asking you, why do you think they are changing it? Is it for your benefit or theirs.

ardara1

fitzie79 wrote: »

I have recently gone to tender to build my bungalow. Got the first quote back today and it is around what we would have expected. However, instead of quoting for what we specified in the tender document they have quoted for their own recommended insulation.

In the tender document we specified the following:

External twin leaf cavity walls to have 60mm rigid Kingspan Hytherm insualtion.
50mm insulated gyproc plaster slabs to internal faces of all external walls

However, they quoted for full fill bead insulation in the cavity. Additionally, they said that they would insulate all underfloor radiator pipework and provide 300mm cellulose pumped insulation to the attic space.

My impression from what I have read is that there are issues with moisture ingressing across the cavity with the pumped bead insulation and that it degrades over time. Would their proposed solution provide inferior performance in both the short and long term?

60 in 100 cavity plus 40 insulation lining U-value - 0.18 - Better insulation value - better thermal bridging details (if fitted properly)

100mm pumped 0.29 - Doesn't meet old regs never mind new - can't verify bridging details - but very cheap

300mm Cellulose - not too sure of lambda value - but should achieve 0.16 approx - but AGAIN very cheap

I'd suggest ask them to tarmac the drive as well and they'll include it in the price.

Do your homework before you decide.


HAVE YOU A BRICK OUTER FACING ON YOUR WALLS?

fitzie79

my initial impression was the same as your rkq. i asked for something so that is what I would expect them to quote for. Fair enough if they wanted to offer what they felt was a better solution but they should quote for both options. My impression though is this that they have quoted for something that is most convenient for them.

thanks for the figures ardara. big difference in the u-values alright. my impression of pumped insulation was that it was ok for upgrading older houses insulation values but not ideal for new builds. i'm not sure what you mean by a brick outer facing on the walls? the walls are predominately plaster on the outside with stone in certain sections

gman2k

They are radically changing the specification here, so ask them to price accordingly.
They would generally be allowed to substitute different manufacturers where you have say spec'ed Kingspan, they can price for an alternate such as Quinntherm.
There is a thread elsewhere about substituting one brand for another (equal approved).
But they are going well beyond this here.
By the way, I'd have no problem with the beaded insulation in the 100mm cavity - if it's by approved installer and fully in conjunction with the certification. But I would want the 50mm insulated slabs internally also.

Quazzie

I have opted for 60mm Xtratherm with 50mm insulated slabs and the remaining cavity pumped. Anyone care to comment on this set up?

RKQ

IMO a clear cavity or air space is important in a wall. Especially on an exposed site or if you have clay brick quoins, heads or elevations.

Without the air gap you are depending on 12 -25mm of render to keep the structure watertight. You could be very lucky, lets hope you are.

I'd have increased the cavity width and explored that option with a Structural Engineer.

Quazzie

thanks RKQ. I considered that but in my particular case my Dad is doing blocklaying so I wanted to keep it was standard as possible for him. I've considered the pumped bead as a little extra but I'll certainly be consulting all the relevant people before actually carrying this out. I'll be weighing up the pro's and con's of both with and without, with the BER guy, before I do anything.