Updating 2 year old plans

Splinter Cell

Hi all! Just got my PP after 2 years convincing the cc I am a local person (site puck of a sliotar from where my grandfather, father and I were born ... go figure :rolleyes:). Anyway, my 2 year old plans do not meet current regs so have engaged eng to update. Basically, 2400 sq. ft story and half, UFH, MHRV, solar for DHW, deciding energy source (oil condenser or wood burning stove). Eng suggests:
Ext walls 100 block, 40 cavity, 100 PIR, 100 block, wet plaster inside
Int walls 100 or 215 block to support conc. 1st floor
Foundation 2 X 60 KS w/ upstand, 150 slab, 60 KS w/ upstand, 75 screed w/ UFH
Not sure about the foundation, my understanding is insulation under slab for thermal store or over slab for response time. Never heard of both combined, says it's a good compromise. I wanted 150 KS over slab with 65 screed for response and ease of build (level with first 215 block for door opes etc.) Any concerns about sagging? Appreciate some opinions - thanks all.

sinnerboy

all proposals have to entered into DEAP software to demonstrate compliance

( that same process will tell you the BER cert result - a separate matter )

a set of specs that worked for one property may not work for another

compliance is a 3 legged stool - take 1 leg away and it falls down

1. the building fabric ( walls/ floors / roof construction including air tightness )

2. the buildings services

3. provision of renewables

you need DEAP calculations to get the mix right

Splinter Cell

While I am here, read about what looks like a great wall build to prevent thermal looping. (sorry for rambling, discovered this forum yesterday and stayed up until 4am this morning reading threads).
100 (102.5?) block outer leaf, 40 cavity, 100 PIR above DPC, 100 extruded PS below DPC, 215 block on flat inner leaf, wet plaster finish. Think it is Sinnerboy's recommendation, should have bookmarked it when I read it . Anyway, my house is L-shaped, i.e. 5m gable (A?) facing to the front with stone finish. This will be a very wide wall, 455 + stone (200?), with 2 x 1100 wide windows. Wondering if looking out the window will be like looking out a tunnel? Anybody built like this yet?

Splinter Cell

Hi Sinnerboy, good timing - you replied while I was posting a second question about your recommended wall build. The eng. will be doing DEAP, BER and supervising/certifying the build. Right now, we are just bouncing around ideas to achieve an A3 rating. He will be redrawing new plans to suit but maintaining the overall appearance, heights etc. to keep in line with the PP.

sinnerboy

Splinter Cell wrote: »

Wondering if looking out the window will be like looking out a tunnel? Anybody built like this yet?

You might look at a reconstituted stone - real stone pieces set into a resin compound to form tiles - can look very good

Check that your PP does not require actual stone first .

Otherwise - yes the windows will have large reveals internally and externally - some like this

It would be good to have an architects eye take a look however . ( I am not touting )

Splinter Cell

sinnerboy wrote: »

You might look at a reconstituted stone - real stone pieces set into a resin compound to form tiles - can look very good

Check that your PP does not require actual stone first .

Otherwise - yes the windows will have large reveals internally and externally - some like this

It would be good to have an architects eye take a look however . ( I am not touting )

PP states stone clad finish, will discuss with the architect. Haven't surprised him with block on flat internal leaf idea yet! Have discussed u-values, aiming for 0.15 floor, 0.20 wall, 0.14 roof or better. Being more careful about good detailing than just chasing u-values. Just reading old thread where you were not in favor of insulation under the floor slab. I am inclined to agree, Engineer's suggestion is mix of both, under and over. Can I ask if that is still your opinion and why? Thanks.

sinnerboy

I assume you are talking UFH ? The insulation must be directly below that . Otherwise you waste energy heating your structural ground floor slab

Edit - re read 1st post - we are talking UFH . Keep all insulation directly below UFH .

Splinter Cell

Yes UFH both floors. That was my thought too, not wasting energy heating the slab. I'll have to adjust his thinking . Any concerns about 65mm screed over 2 x KS boards = 150mm insulation - sagging or cracking?

Restricted to < 7m ground level to ridge height so planned for < 300mm ceiling, i.e. 100mm suspended ceiling for MHRV ducting, 100mm slab, 25mm insulation w/ upturn and 65mm screed.
Is 25mm insulation ok or should I go more and use a thinner screed like the easy flow stuff?

Thanks for all the suggestions, you seem to be helping a lot of people on this forum!

sinnerboy

Ground Floor
2 x 75 ins + 75 screed will course to block + joint 215 +10
No concern for sagging if you select ins intended for purpose

upper floor
if you are restricted to 300 overall upper floor - forget concrete there
100 slab wont work - min 200 possibly 250 ( 200 slab + 50 screed )
Ducts are typically 125mm and will require insulation wrap

Consider eco joist timber joists ( google it ) to accommodate HRV ducts .
25 insulation over timber deck + 40 easy flow would be fine .

you may need - even with this spec - settle for 350-375 overall floor
( ceiling - to - upper-floor-finish )

Splinter Cell

sinnerboy wrote: »

Consider eco joist timber joists ( google it ) to accommodate HRV ducts .
25 insulation over timber deck + 40 easy flow would be fine.

Thanks Sinnerboy, interesting alternative, had never heard of it. My max spans are < 5M, quick look at the specs suggests it will work. Will do more research and call some vendors.

Re: the concrete alternative. I contacted a concrete manufacturer from your neck of the woods (Meath) who I can't mention (hint: what you get after a deluge of rain ) that can supply 100mm wideslab. This combined with 25mm insulation, 75mm screed w/ UFH and 200mm x 60mm rigid duct from a HRV manufacturer in Galway appears to work on paper at least. I thought the ducting was only insulated in the attic? Have I overlooked something else?

sinnerboy

http://www.sap-appendixq.org.uk/documents/MVHR_Installation_Guide_Final.pdf

flat ducts will increase resistance - i.e. require more fan energy - to distribute air . the efficiency of the installation will be badly affected

circular ducts minimize resistance

ducts in unheated voids should be insulated . My opinion - this includes a first floor void as well as the attic space

ask your engineer about the concrete upper floor structure