MVHR with a warm flat roof and loft floor insulation?

[Pseusmyd]

I am currently converting my bungalow into a 4 bed house including a flat roof of around 35m2. This flat roof has been designed by the architect as a warm roof. It will be well insulated but not passive. A flat roof had to be installed vs a pitch roof due to planning restrictions.
 

Below the flat roof will be a “mini” loft of around 900mm height. This loft will hold both supply and extract manifolds and ducting running towards the rooms. De loft has been designed by the architect without insulation between the bedrooms and the loft, just plasterboard on 2x4 joists. My builder has suggested to install insulation in the loft floor to reduce heat transfer from bedrooms to loft.
 

if I could pick your brain, would this loft floor insulation affect the “warm” loft and the uninsulated manifold and ducting? Has anyone has any experience with a warm room and a insulated loft floor.

 

Any suggestions or comments are appreciated.

 

 

 

[AliG]

Assuming the roof is well insulated this would just be extra work and probably a waste of money. Although if you used say 37.5mm insulated plasterboard, it would probably only cost you around an extra £10 a square metre. Of course this also slightly reduces your ceiling height.

 

If you insulate below the ducting the ducting may have to be insulated as we found out when we changed some area of loft from eaves level to ceiling level insulation. The savings mostly disappeared when we had to insulate the ducting. You might be OK as there s still insulation above it, but this would be my main concern.

[ProDave]

Yes keep the loft warm, i.e. no insulation above the bedrooms.

 

Having just built a 1.5 storey house with a warm roof I would say having a warm roof is the single biggest improvement over any house i have previously owned in terms of ease of build, ease of detailing insulation and air tightness and performance.

[the_r_sole]

If you've got 900mm "loft" could you not just have a taller room? Add another 600 on to the room and still have 300mm for ducting?

[Pseusmyd]

All, thank you for your comments and suggestions.

 

it makes sense not to insulate the loft floor and I will “ignore” my builders recommendation ref the additional insulation.

 

@the_r_sole Your idea makes sense but senior management at home decided it was a must for her to have a mini loft for storage space... The rooms will be still 2m45 height so not too bad.

 

 

[the_r_sole]

9 hours ago, Pseusmyd said:

All, thank you for your comments and suggestions.

 

it makes sense not to insulate the loft floor and I will “ignore” my builders recommendation ref the additional insulation.

 

@the_r_sole Your idea makes sense but senior management at home decided it was a must for her to have a mini loft for storage space... The rooms will be still 2m45 height so not too bad.

 

 

put a cupboard somewhere, much more useful than a weird loft store! ?