Church renovation - UFH design

[ChurchAl]

Morning, we are looking at UFH for an open plan living space (Kitchen, living, diner) in a church we are renovating.

 

Working out what system to use at the moment, given we are retrofitting the timber suspended floor with insulation, we reckon a structural deck with routed pipe grooves seems sensible. Covered with 6mm ply and to be finished with an engineered timber.

 

Given the approx demand of 5kW, I am looking at 16mm pipes at 150mm spacings with 5 circuits to stay under the max 100m individual circuit length (1 zone though). I will attached a floor plan for awareness.

 

Any comments/guidance on the above including proposed layout would be greatly appreciated.

 

Other Spec:

• Area: ~75m2
• Ceiling height: 3m majority. 25m2 has 6m ceiling height.
• Floor: Suspended Timber insulated with 140mm Steico Woodfibre.
• Walls: Solid stone, insulated 100mm Steico Woodfibre
• Glazing: Significantly large church windows however secondary glazing is being installed across all.

[ProDave]

A few general points.

 

I am not convinced 140mm of insulation in the floor is enough, I have 300mm in mine.

 

You want a means to spread the heat from the pipes, not just bare pipes. So spreader plates or create a 25mm void to lay the pipes in and fill with biscuit mix sand / cement before the final floor goes on.

 

Is the wood fibre wall insulation going inside or outside?

 

You mention a 6m high space above the kitchen, how large is that area?  I can see a lot of heat going up there.

[JohnMo]

I would really concentrate on how get to best heat transfer from pipes to floor. Do it wrong and system performance will be poor. An option is a biscuit mix. Poor heat transfer will require higher flow temperature for the same heat output to room. Not sure your proposal will be good enough, wood is a good insulation so heat transfer not the best. You also need zero air gaps around the pipes. Every air gap will diminish heat transfer opportunity.

 

Get as much insulation in the floor as possible 140mm wood fibre should really be increased to 200mm+.

[Redbeard]

29 minutes ago, ProDave said:

I am not convinced 140mm of insulation in the floor is enough, I have 300mm in mine.

 

 

30 minutes ago, JohnMo said:

 

Get as much insulation in the floor as possible 140mm wood fibre should really be increased to 200mm+.

Agreed. How much clearance/crawl-space do you have below the joists? If you can 'underdraw' with further insulation then you can also 'cloak' the thermal bridge of the joists. I'd go for as close to 300 as you can. Although the temp differential between room temp and 'outside' (under-floor) may be only 21 or so at 0 degrees external, the temp diff between the flow and the ext temp will likely be a minimum of 40.

[saveasteading]

I'm moderately happy at 150mm depth but pir not woodfibre.

There is diminishing return after that, esp if you are turning the heating off at times.

But then on top you have an option of material. There is a 22mm ? Eps panel system with pipe grooves already in it.

Or simply pin the pipes to the pir.

Then pour self levelling screed 40mm or more over the top.

 

But thicker insulation is better obviously.

And i agree about stuffing under the floor if you have access.

[ChurchAl]

@ProDave@JohnMo@Redbeard@saveasteading: Thanks for the input. I agree more insulation would be better; we would look to add additional wood-fibre if possible however we don't know for certain joists depths across the whole area, we are yet to complete on property (exchanged so far) so can't go ripping the existing floor up to see. I'm basing the 140mm off of assumed depth from joists which I can see in a different room. I will certainly fill the space though if deeper! I have not heard/seen filling below the joists of a G-floor suspended floor before so not even considered that... I assume as long as clearance is good and vents are unobstructed, insulating deeper than joists is ok?

 

@ProDave I have seen the spreader plates before... you reckon worth the money? Woodfibre insulation is internal for walls, hence part of the desire for UFH to avoid rad mounting faff in the open plan area! Vaulted area is 1/3 of the area - approx 25m2.

 

@Redbeard Once we can get boards up and see the space ill know if underdrawing is an option, but thanks I had not even considered that!

 

@saveasteading I am trying to avoid all PIR/non breathable options so looks like increased insulation between and below is the best COA. EPS isn't breathable from what I can see?

 

What were thoughts on rest of the proposal? pipe sizing, loops etc?

 

 

[saveasteading]

9 minutes ago, ChurchAl said:

insulating deeper than joists is ok?

 

But no point. The joists themselves are the thermal weakness.

 

10 minutes ago, ChurchAl said:

pipe sizing, loops etc?

Suppliers will do that for you, but assume 16mm pipes at 150cc.

 

11 minutes ago, ChurchAl said:

trying to avoid all PIR/non breathable options 

 

I like your principle, but if it's re "carbon" then the lifetime of reduced heat loss prevails.

If it is because celotex and kingspan should be avoided on business ethics then I agree, but there are others.

But for being breathable? I'd have to think on that.

[Redbeard]

Is it single-storey?

[Redbeard]

Just now, saveasteading said:

16 minutes ago, ChurchAl said:

insulating deeper than joists is ok?

 

But no point. The joists themselves are the thermal weakness.

 

Agree if you just 'posted' deeper WF to hang below the joists, leaving the joist bottoms 'naked', but my hope is that there is sufficient crawl space for a cross-layer of rigid WF underneath (or flexi WF in a form of 'Larsen Truss' (spaced joist, @ChurchAl, if you haven't come across the term before)). That way the thermal bridge is mitigated.

[ChurchAl]

2 hours ago, saveasteading said:

But for being breathable? I'd have to think on that.

This was the main consideration based off of what I have read and experience with projects in the past. Carbon/ natural use second. Not heard about the ethics of the PIR big firms but I imagine that'll be a thread of its own somewhere!

 

2 hours ago, saveasteading said:

Suppliers will do that for you, but assume 16mm pipes at 150cc.

Happy - just trying to get a feel/idea before I get quotes/spec.

 

2 hours ago, Redbeard said:

Is it single-storey?

No, 2/3 of the area above the central area which is having the UFH is first floored.

 

2 hours ago, Redbeard said:

Agree if you just 'posted' deeper WF to hang below the joists, leaving the joist bottoms 'naked', but my hope is that there is sufficient crawl space for a cross-layer of rigid WF underneath (or flexi WF in a form of 'Larsen Truss' (spaced joist, @ChurchAl, if you haven't come across the term before)). That way the thermal bridge is mitigated.

Understood, I assumed this is what was meant as opposed to leaving thicker WF protruding from the base of the joists - It will come down to space realistically (and the cost in part).