Second heat source after underfloor heating

[nirish]

As mentioned in another thread we have a vaulted ceiling garage conversion with underfloor heating. The underfloor is running hot at almost 60deg flow. When it's mild outside it heats the room to a lovely 21deg but when it's cold we can't get above 18deg. It appears nothing further can be done with the underfloor which was the previous discussion.

I'm furious about the whole thing given how much I spent on the underfloor but now I need to focus on solutions of how best to supplement the heat source.

Any ideas and how it would work in conjunction with the underfloor welcome.

We do have an electric fire in place but primarily for it's fake flame look, I hadn't intended using it as a heat source as I assume it's an expensive solution!

 

[BlueLoo]

I can't imagine UFH would have enough umph to heat a garage conversion, especially one with a vaulted ceiling!
I mean, yeh, it could work but......

Is the conversion properly insulated? the less you lose the less you need.
Perhaps having the building propelry insulated (if it isn't) will not only get the place warm, but will justify the UFH.

Just a thought.

 

[nirish]

@BlueLoo yes I'm furious the experts installed it and never mentioned that this would be an issue but that's where I am now. I don't know what thickness but Celotex was installed in all walls and ceiling so doubt I can do anything there.

It appears I'm stuck with adding more heat so that's what I'm looking at unless another miracle arises!

 

[oldbutnotdead]

Assuming your wet UFH is heated by gas or oil, additional radiators will be the most cost-effective long term fix. You might want to buy a cheap freestanding 2kw convector heater (or a beefy oilfilled rad if such things exist) and test positions for it before you start running tube in.

 

[BlueLoo]

@BlueLoo yes I'm furious the experts installed it and never mentioned that this would be an issue but that's where I am now. I don't know what thickness but Celotex was installed in all walls and ceiling so doubt I can do anything there.

It appears I'm stuck with adding more heat so that's what I'm looking at unless another miracle arises!

I've just read your other thread.

I'd see if you can get a building engineer to inspect the system/building and see if everything is working ok.
If so, and its simply that your building has too much heat loss, then, you either have to cure the heatloss or up the input.

How about a wood stove?

 

[snb]

i have fitted hundreds of underfloor systems and many in barn conversions with vaulted ceilings that are sometimes 50ft high. Never had any issues. But it does depend upon your floor coverings. If you have wooden floors then you are going to struggle badly, unless you are running flow temps near to 50c

 

[nirish]

My concern with the rad solution is that if I want extra heat on a given day I assume I'll have to fire up the rads in the rest of the house at the same time.

I had been wondering about a log burner for some swift additional heat when required. The potential cost given what I've already spent on the underfloor is putting me off but I guess I just need to get to the past that point!

Improving heatloss sounds preferable but I've no idea how that could be achieved in a completely finished, plastered and painted room!

 

[oldbutnotdead]

Not these days with programmable TRVs- every rad can be its own zone

 

[nirish]

@snb the flow temp is currently 55° and sometimes higher, nowhere near the efficiency I'd hoped for. Over the pipes is a thin screed, chipboard, 9mm ply and Karndean. In retrospect perhaps there is too much wood but I don't know how it could have been done differently. Surface temp today is 22°-23°

I suspect the vaulted aspect isn't the issue, three external walls and plenty of windows doesn't help! I just wish this had been forseen but we are where we are!

 

[snb]

should have been screeded with karndean straight on top of screed. You would be best to rip the flooring out. Have another 20mm of poured screed applied on top of the existing screed and then put you finish straight on top. Your chipboard and ply are acting as insulation above the heat source.
You should be able to tee into the underfloor set up to connect a radiator or two. You will probably be surprised how little extra heat is needed to get your temp where you want it. I would try a fan heater on 1kw setting and see the effect.

I have a few underfloor setups where they have a couple of towel rads connected as well. They work fine so it should be possible for larger rads. Just flow temp will be at underfloor temp.

 

[BlueLoo]

As an idea.

Whilst the wood is insulating the heat from the room, its also limiting the total heat output of the system. (Imagine your return temps are higher than youd expect).

Just tap off the ufh with a large radiator. Your heat input into the room should then revert to what the ufh was designed for.

However, id still go back and do a 1st principles heat balance on the building. You might find that regardless of the floor, it was never enough to heat it anyway.

 

[nirish]

@snb I'm a bit confused as surely the kardean can't be laid straight onto the screed? It must need ply or something similar to fit it to? At this point the parquet karndean cost 1k to fit to the thought of ripping it up to remove some wood and relay it is quite a painful one.

Interesting to hear two suggestions of running radiators off the underfloor! I assume this would be at minimal extra running cost but bring some of the underflow heat above surface level?

 

[nirish]

@snb I have an electric fireplace in the room rated at 1500W. I had never intended to use it for heat, just it's glass box flame effect.

However for the purpose of your test I could use it to see if it's enough additional output to heat the room. How long to run it to see if it makes up the difference?

 

[snb]

Normally you would lay karndean onto the screed. With underfloor heating you normally latex it first so it can absorb the thermal movement. Don’t know why someone told you to use ply and hardboard.

as for testing the extra heating. With underfloor you need to run it for a minimum of 18 hrs per day and allow the thermostat to control any off times. Ideally you would run it 24hrs and allow the thermostat to control the off periods. To test how much extra heat I would run the electric heater for around 8 hrs and see the effect

 

[nirish]

@snb it's a joisted floor, celotex was laid between the joists and the underfloor clipped to the insulation as per the pictures. They weren't going to screed but I asked them too, so they added a thin layer up to joist height.

The builder then added 18mm chipboard.
Later the Karndean fitter laid 9mm ply on top before the Karndean itself.

I'm confused by the heat test? Run the underfloor with a demand of 21deg for 18hrs? What do you mean by let themo control off times, it isn't getting above 18deg on cold days. 8hrs of the electric, ok wow, longer than anticipated!