Question about UFH and ASHP

[Joshua Graham]

Hi, new member here, but have been reading this forum for a while. Currently renovating a 60s property as my first home. I am getting an air source heat pump installed, as oil is no longer a financially viable option. I want to run my heat pump at 35 to heat the house using underfloor heating on the ground floor. The ground floor is suspended timber floor, with new sheets of chipboard down. I have been looking into systems that you can lay atop the existing floor and was looking for advice as to what type of pipe centers for this as some places have said 100mm but there are no products out there that do pipe centers this close! I think its worth noting I have underfloor insulation of 60mm of pir and 150mm of mineral wool, and a membrane to protect against drafts, 600mm mineral wool in eves and bead cavity filling. I have also filled any openings i could find, to prevent air leaks. Are 100mm center overkill? If not, could I cnc the center my self into my existing chipboard floor or a layer on top of the existing chipboard then lay 6mm of ply?

 

Thanks

 

JG

[Andehh]

150mm is fine, 100mm risks the bend radius being a real headache! 

[JohnMo]

You cannot just pick a flow temperature and assume it will work.  Flow temp depends on heat loss, both from the house and downwards.

 

You really need to be looking at running weather compensation to get the best CoP.

 

See attached, the red lines are there as examples.

 

You need to calculate your heat loss then find W per m2.  From these charts you can calculate your heat for WC.  Find heat loss at -20 and +20, convert them to flow temps and plot a straight line curve.

 

 

You need to consider the min flow requirements of the heat pump and let that guide you on centers.  Also the centre distance affects the response time of the floor.

[PeterW]

Agree with the above, plus you need blender / buffer as your ASHP has to either modulate all the way down to the lowest heat emitter (ie shortest loop) or it will short cycle. And don’t rely on the ASHP pump to circulate the UFH..

 

@Joshua Graham you don’t say what final floor finish will be - that will affect your choice of system you use.

[Joshua Graham]

I should have said the floor type is engineered oak, 10mm depth, the system uses a valiant unitower to.

[spottycat]

Joshua,

 

Not sure if this is of any help with your query but food for thought even if you do something different. Several years ago I install UFH on my first floor but wanted to ensure the best possible heat transfer. i did something a bit unusual but am still happy with my results. I am still working on all the page for my ECO house restoration blog but the page on UFH is on my DIY Home extension blog if you want to read it and see what I did - https://diyhomeextension.co.uk/first-floor-ufh/. Good luck with whatever you decide.