Partial fill cavity construction: dead?

How much of a correction is required for the larger\more frequent wall ties in a 150mm cavity?
 
Hi Sydthebeat,

You're in demand tonight! Could you advise what insulation to use for the downstairs floor - we will be going for UFH. Upstairs using concrete floors - unsure whether to go for UFH or rads upstairs - at this stage we have 70% the heat source to power the UFH will be a WPB.

Thanks in advance

Angela
 
sas said:
How much of a correction is required for the larger\more frequent wall ties in a 150mm cavity?
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working off the top of my head here, the wall ties increas from roughly 3 per sq m to 4.9 per sq m.
the calcs i do have the wall tie factor applied, i havent yet figured out how to increase this factor by 63%... but i dont expect it to be significant... possible 3-4% of the U Value.

angela.. can i leave your question till monday.....
can you specify your UFH manufacturer
 
Hi Sydthebeat,

We are hoping to go for WPB either Windhanger or KWB haven't decided but we are hoping to for a very good german or austrian brand.

Many thanks

Angela
 
Was at the Self Build Expo in Belfast today... more later in the year around the country and would highly recommend to all!!
 
 
Most of this is going over my head, Getting an extension at moment.Double extension with attic conversion. House was built 1940's with hand made soild conrete blocks and I mean blocks. Took out a few internally and with the sand&cement and skim on them they were huge.

My house is terraced and have tossle walls with a sub floor, the extension the builders are doing a 100mm outerleaf,50mm cavity with kingspan insulation,100mm innerleaf with sand&cement then skim I think....

Have had numerous people telling me, this won't cut the mustard in the U value rating...Would I be better to say to builders to extend the 50mm cavity to 100mm? Is the AAC blocks expensive and where would you source them.
 
mad m said:
Have had numerous people telling me, this won't cut the mustard in the U value rating...Would I be better to say to builders to extend the 50mm cavity to 100mm? Is the AAC blocks expensive and where would you source them.
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Hi mad m, I'm no expert but a 50mm cavity doesn't give you much room for insulation. If the cavity is 50mm what width is the insulation... 20mm? 60mm of insulation is the standard but this would be a minimum these days now. The normal cavity is 100-110mm so I would say increase to this and then increase the amount of insulation... either solid board or even bonded bead which packs the entire cavity. I'm no expert though and to be honest for a few quid it would do no harm to get some professional advice.... you'll only build it once but heat it for a lifetime!!
 
Just checked before they start. They have 4 inch solid,4 and half inch cavity and then another 4 inch solid....Can you fill the whole cavity with beads? whats the minimum the insulation has to be away from the outerleaf 100mm solid...
 
mad m said:
Just checked before they start. They have 4 inch solid,4 and half inch cavity and then another 4 inch solid....Can you fill the whole cavity with beads? whats the minimum the insulation has to be away from the outerleaf 100mm solid...
Click to expand...

Yes you can fill the entire cavity with blown in beads. This has the advantage of getting more insulation around your build and (as long as it's blown in correctly) packing every space. Unless your builder takes great care, the rigid boards will not sit flush with the inside wall so it will significantly reduce the effectiveness of the insulation. The builder should also reduce the price significantly as it makes his job much much faster and easier €€€ You can also use both rigid insulation and beads by the way.

Anyway I would suggest you read this entire thread as there's loads of very useful info regarding the merits of using bonded bead, rigid insulation or indeed both.
 
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