New House advice

Kanu78

Hi everyone. We're about to turn sod on a new storey and half type house and I'm looking for people's opinions on my building ideas. Firstly, we've decided to go the geothermal route to heat the house, with horizontal piping. The house is approx. 3000sq ft and we've been told that a 11KW Bosch heat pump should suffice. We're going with underfloor heating downstairs and upstairs and plan to put a stove in the sitting room and kitchen, with a chimney closer in the living room for the seldom occasions it'll be used. We've been quoted 26000 for all the heating and plumbing. The blockwork specfied is 100mm outer leaf, 140mm cavity and 225mm inner leaf to support concrete flooring upstairs. We intend putting 100mm of rigid insulation in the cavity and possibly pumping the remaining 40mm afterwards. I don't think we will go with the thermal liners on the internal walls as I hope they will act as a thermal mass without them. Or we may put them on north facing walls. I also plan to use 150mm of insulation in the floor. Our heating guy is pushing the heat recovery on us a bit but I think we'll give it a miss. It's working out at 5,500 euro. Regarding the windows, we plan to use aluclad on the back and sides with sliding sash on the front. I know they're not airtight but we love the look of them and plan to put extra seals on them. Anyway, any opinions or advice you have on our early plans would be greatly appreciated.

sydthebeat

cavity pumping is only certified for cavities of 50mm or greater.

also, it doesnt make economic sense to have two types of insulation in the one cavity...
150 cavity pumped would, in my opinion, perform better than 100 board insulation and 50 pumped...even though on paper it may show a better u value.

on the heat recovery... see it like this. your living room is heated by your UFH. the 'hole in the wall' vent changes the air 4 times in every hour, on a standard day with say 15 mph winds.
That means that your UFH needs to heat the room 4 times in every hour.

if you have a MHRV which is running at say 75% (which would be pretty poor performance) the you only need to heat the room once every 4 hours.

so thats 16 times less fuel used with MHRV.

add on top of that the comfort factor and the draught less factor ....

Kanu78

Thanks Syd. Interesting that you're keen on the heat recovery too, maybe we should look more into it. I'm just a bit concerned that it won't work as well in the rooms where we're putting the sliding sash windows. And thanks for your advice regarding the cavity walls. It's a bit of a dilemna how to insulate them. Would you recommend the full-fill cavitytherm boards instead? My blocklayer is excellent which I know is important.

fclauson

How do you intend to meet Part L with the build spec you propose
and
Have you had a provisional BER done

I am only guessing but you are going to struggel to comply

Kanu78

we intend putting trickle vents in our windows. these meet regulations without the expense of a heat recovery system

fclauson

nope - I am talking about your wall and floor

the floor needs to be less that 0.15 U for UFH
and the walls with 100mm I think will not hit target

please do get a BER done before you lay a single block

kboc

Kanu78 wrote: »

we intend putting trickle vents in our windows. these meet regulations without the expense of a heat recovery system

trickle vents are dead and buried in a well insulated air tight house. I think you are putting the cart before the horse by talking about Heat pumps.

If I were you I would engage somebody to assess the energy demands of your future house and then use this info to make informed decisions.

There is some of these "somebodies" on this forum who know their onions and well worth PMing and asking for the required help.

good luck