starting blocks in 2 weeks, pumped cavity?

hello All,

we are starting blocks in 2 weeks, its the basic 100mm outer leaf, 100 cavity, 100 inner leaf, we are going to insulate the internal walls with slabs backed with insulation,

We were going to go with standard 60mm kingspan, however a friend has told us that pumped cavity would be way better, i am a little worried about rising damp within the cavity if its pumpted?

Any suggestions im hearing around 1200 -1400 hundred for the pumped cavity, house 2260 sq foot story and a half.

secondly if i go with the pumped option do i need to do anything else? damp proof course on bottom layer?

I am not sure but do Kingspan have a technical advisor who can do the maths for u... They seem to have mastered the art of insulation..

I know of people who pumped the cavities of older houses which didn't have insulation but I have never heard of pumping the cavity of a new house....

A friend of mine got a layer of Kingspan on the outside of the house which is plastered over - he is an out an out Green so I'm assuming that he was doing this for optimum insulation.... However when u tap the plaster you hear a hollow sound and it seems that with enough hard knocks the plaster could crack.

I'd ring Kingspan and also the people who pump and weigh up the two options..

pumping the cavity would be the best option . dampness wont be an issue as i did my house which has brick on the outside. three winters later still no problem

Hi CSMD,

Can you state why you think pumped cavity is better? I am at the same stage and am thinking of going with Kingspan. Reason: I have heard that if the blocklayer drops mortar down the cavity it can block up spaces where the cavity fill shoulb be????

I haven't a clue really. Just interested to hear why you think it's better.

Btw, both have a u-value of .27 (silver beads and Kingspan TW70). Both are coming in at simialr prices give or take a few bob. I also plan to dryline (now that's where the expense comes in!!)

rang kingspan today and am now going with 60mm TW50 plus 38 mm board on the inside, couldn't justify the K8 board on cost, mush better to put the money inside the wall, they are very helpful,

Take a look at this previous thread for a discussion on partial fill versus pumped cavity insulation.
Leo

Yes the thread, referenced by Leo is very useful. Personally I would go with a wider cavity but I suppose it's too late for you now that the foundations are in?

If you cannot change the cavity width, then how about using an AAC block (e.g. QuinnLite) for the inner leaf. Also I would go ahead with the rigid Kingspan board but would also pump with beads. That would give you 3 layers of insulation compared with the one layer you are looking at at the moment. There's a tool on the sei.ie website that will allow you to calculate the u value of such a wall.

By dry lining you can add a 4th layer but the cost may not be worth it, anyway that's something to consider later anyway.

BarneyMc said:

Yes the thread, referenced by Leo is very useful. Personally I would go with a wider cavity but I suppose it's too late for you now that the foundations are in?

If you cannot change the cavity width, then how about using an AAC block (e.g. QuinnLite) for the inner leaf. Also I would go ahead with the rigid Kingspan board but would also pump with beads. That would give you 3 layers of insulation compared with the one layer you are looking at at the moment. There's a tool on the sei.ie website that will allow you to calculate the u value of such a wall.

By dry lining you can add a 4th layer but the cost may not be worth it, anyway that's something to consider later anyway.

Click to expand...

The foundations should be fine if you want to increase the cavity width. You are not actually increasing the loading on the founds by increasing the cavity.