Insulation on first floor

JD6910

i plan to install UFH on ground floor. i have 150MM precast slabs on first floor. i plan to do full airtightness and really watch the thermal bridging details.

i also plan to install a heat pump and a MHRV system.

just wondering will the MHRV be sufficent for my upstairs heating requirements as the house will be insulated way beyond the standards and have full airtightness???

is putting UFH upstairs madness when in reality we will be at work all day!!!

about2build

Describe the level of insulation and the target airtightness at Q50? MVHR is not a heating mechanism but a ventilating one....it retains (75%) ish of heat being exchanged to the outside but not create heat in itself....ufh upstairs might be overkill ...I am going with rads but on a separate loop that can be cut out...but you will need something up there

JD6910

the insulation in summary at the moment is 200MM SD EPS in the floor, 200MM full fill cavity bead, roof will be most likely spray foam with 50MM rigid board on the outside of the rafter with ventialtion outside the felt by means of counter battening. in relation to airtightness going to try get it as best as i possibly can within the budget available at thst stage of the build.

i agree with what you say about MVHR system but also is it fair to say is distributes heat from showers, kitchen etc... into areas like bedrooms?

Maybe the UFH on the ground floor will contribute to heat upstairs if i omit the insulation between the first floor???

i think maybe UFH downstairs and rads upstairs which can be controlled seperately is the sensible approach. i cannot see the reasoning for UFH upstairs when nobody is upstairs all day and when we do go upstairs we jump under the duvet!!!!!

sydthebeat

JD6910 wrote: »

the insulation in summary at the moment is 200MM SD EPS in the floor, 200MM full fill cavity bead, roof will be most likely spray foam with 50MM rigid board on the outside of the rafter with ventialtion outside the felt by means of counter battening. in relation to airtightness going to try get it as best as i possibly can within the budget available at thst stage of the build.

i agree with what you say about MVHR system but also is it fair to say is distributes heat from showers, kitchen etc... into areas like bedrooms?

Maybe the UFH on the ground floor will contribute to heat upstairs if i omit the insulation between the first floor???

i think maybe UFH downstairs and rads upstairs which can be controlled seperately is the sensible approach. i cannot see the reasoning for UFH upstairs when nobody is upstairs all day and when we do go upstairs we jump under the duvet!!!!!

the bit i bolded makes no sense.
what is your roof makeup from inside finish to outside air?

about2build

Agree with syd. Also the problem with underfloor heating is the delay in it being turned on to when the heat is radiated to the room...defo the ufh downstairs will have a heating effect upstairs and when as you say you are under the duvet you dont need anymore than a modicum of heat say 14 degrees. I am not going for ufh and will have the rads like i said that can be shut off on a separate loop and with the levels of insulation you have outlined, presuming you reacha an airtightness of less than 2 @ Q50, then you should have no need either IMHO

JD6910

from the inside: 12.5MM plasterboard. airtightness membrane.i will be putting in 225MM rafters, sprayed full depth with spray foam insulation. i will be putting 50MM insulation outside the rafter battening the rafter and then counter battening to form my ventilation space. the battens will hold the insualtion in place. windtight felt layer which will be taped and then slate will then be fixed to battens. it is known as warm roof construction.

any thoughts??

sydthebeat

JD6910 wrote: »

from the inside: 12.5MM plasterboard. airtightness membrane.i will be putting in 225MM rafters, sprayed full depth with spray foam insulation. i will be putting 50MM insulation outside the rafter battening the rafter and then counter battening to form my ventilation space. the battens will hold the insualtion in place. windtight felt layer which will be taped and then slate will then be fixed to battens. it is known as warm roof construction.

any thoughts??

the roofing felt is to be placed between the batten layers.
the ventilation space you are creating will be between this felt and the under batten layer.
Venting this is a good idea, although the risk of moisture damage to structural timbers is lessened with this type of construction as the dew point exists out side the rafter level.

JD6910

JD6910 wrote: »

i plan to install UFH on ground floor. i have 150MM precast slabs on first floor. i plan to do full airtightness and really watch the thermal bridging details.

i also plan to install a heat pump and a MHRV system.

just wondering will the MHRV be sufficent for my upstairs heating requirements as the house will be insulated way beyond the standards and have full airtightness???

is putting UFH upstairs madness when in reality we will be at work all day!!!

so to go back the the question???????:rolleyes:

sas

JD6910 wrote: »

so to go back the the question???????:rolleyes:

The issue here is that you're saying your using lots of insulation, doing good airtightness detailing etc. To advise properly people would need to know the
heat load has your house been designed to.

I've UFH downstairs.
Upstairs I've hollowcore with no insulation and no UFH.
I shouldn't need anything up stairs due to the passive nature of the house.
However, I did put provision in the attic space (i.e. flow and return) for rads which can be retrofitted to each bedroom if needs be.

JD6910

sas - thanks for the advice.

who typically calculates the heat load?? plumber??

sas

JD6910 wrote: »

from the inside: 12.5MM plasterboard. airtightness membrane.i will be putting in 225MM rafters, sprayed full depth with spray foam insulation. i will be putting 50MM insulation outside the rafter battening the rafter and then counter battening to form my ventilation space. the battens will hold the insualtion in place. windtight felt layer which will be taped and then slate will then be fixed to battens. it is known as warm roof construction.

any thoughts??

Either you've described it badly or you're not doing a typical warm roof build up as I understand it.

From the inside to rafters being sprayed its fine (I don't like spray insulation but that's another conversation).
Then it's:
- Insulation outside rafters.
- Felt taped for wind tightness
- Batten parallel to rafters
- Slating\Tiling batten
- Slate\Tile

This is what I was advised to do by the suppliers of the materials that make up my warm roof



As described you've a ventilation gap beneath the felt making the taping of the felt somewhat pointless.

sas

JD6910 wrote: »

sas - thanks for the advice.

who typically calculates the heat load?? plumber??

Lord no.

It's done either using the DEAP software through a BER assessor or preferably through the PHPP software by a certified passive house planner\designer.

sydthebeat

JD6910 wrote: »

sas - thanks for the advice.

who typically calculates the heat load?? plumber??

JD6910

going by a lot of your previous posts (suppliers offering u values etc) you dont seem to have any professional engaged to advise you, either that or they're not doing their job... why not?

see the forum charter:
1.0 Overview

1.1 This board is intended for discussion of Construction & Planning issues, by fellow users, and as a place to openly exchange tips and advice for free i.e. no one must seek to gain personally, professionally or financially from their participation in the forum . It is not a consultancy service and it is strongly advised that you always appoint your own professional advisor(s). Be aware that being an open public forum you may not always get exactly the response you would hope for. You will find that there are plenty of posters who will help you here but if you don't like some posts or posters try to pass over them .

JD6910

sas - many thanks. can you PM me more photos please. looks like your been there and done that!!!!

sas

JD6910 wrote: »

sas - many thanks. can you PM me more photos please. looks like your been there and done that!!!!

Any photo of use that I have is already on the "Live Self Builds" thread.