GSHP with UFH

[Dan1983]

Morning all,

quick question regarding house heating If possible.

Builder is currently sorting a quote and suggested GSHP and UFH on both floors.

we generally run our thermostat at 18 degrees C in our drafty bungalow with normal radiators all year round.

From reading up I’m worried a GSHP may struggle to keep the house nice and warm in the winter and also taking a while to warm up if using it with UFH vs a normal gas combi/ rad set up.

Has anyone gone this route from a traditional heating system?

As our current house has always been quite cold I’d hate go a new route and end up with a chilli house again!

 

cheers for any pointers

  

[scottishjohn]

8 minutes ago, Dan1983 said:

Morning all,

quick question regarding house heating If possible.

Builder is currently sorting a quote and suggested GSHP and UFH on both floors.

we generally run our thermostat at 18 degrees C in our drafty bungalow with normal radiators all year round.

From reading up I’m worried a GSHP may struggle to keep the house nice and warm in the winter and also taking a while to warm up if using it with UFH vs a normal gas combi/ rad set up.

Has anyone gone this route from a traditional heating system?

As our current house has always been quite cold I’d hate go a new route and end up with a chilli house again!

 

cheers for any pointers

  

the first thing you should be spending on is sorting the drafty leaky fabric of the house out

then how you heat it is secondary 

what i will say is GSHP is not going to be best option in uk --cost will be far more exspenive than ASHP

GSHP only has an adsvantage in very cold dounctris like canada where you get months of -15c and the fact that the ground will stay a constant temp makes the gshp COP rate a winner 

but not in our mild climate

but neither should be used with a poor building 

[SteamyTea]

With any heating system it had to be sized correctly.

As heat pumps generally operate at a lower temperature, the emitters, radiators, under floor pipes, duct heaters or whatever, generally need to be larger (pipes closer together in UFH).

GSHP tend to be more expensive to fit and offer little advantage over ASHPs. Though though tend not to freeze up in damp, cold weather, bit of an over stated problem in my opinion.

It is worth getting someone that really knows about heat pumps to do the calculations.

[Dan1983]

Ok thanks for advice,

For info the install would be going into a new build house not the current bungalow.

Think I’m tempted to stick with the norm using a combi boiler 

[ProDave]

6 minutes ago, Dan1983 said:

Ok thanks for advice,

For info the install would be going into a new build house not the current bungalow.

Think I’m tempted to stick with the norm using a combi boiler 

That changes the question. A new house should not be cold a draughty like the old one, so UFH should work well.  The decidion should be ASHP or GSHP.  you will find the costs of ground source a lot higher than air source for only a small decrease in running costs.

[Dan1983]

Cheers Dave,

i have just been having a read up, think I’m tempted to spec ASHP as seems easier to install plus advantage of being able to work in reverse.

guessing the newer systems are fairly quiet now compared to the older ones?

Bedrooms and lounge are going to be carpet so not sure if that effects the heat transfer of UFH? 

Edited February 13, 2020 by Dan1983

[Dreadnaught]

6 minutes ago, Dan1983 said:

Bedrooms and lounge are going to be carpet so not sure if that effects the [heat] transfer of UFH?

 

UFH guidance gives a Tog limit for the carpet insulative power. I have seen the figure 2.5 Tog used regularly in this regard. (It should be Tog total of both the carpet and its underlay.)

[ProDave]

A lot of us find in a well insulated air tight house, you don't actually need any heating upstairs.  I am at least the third on here that I know fitted dedicated electric points in the bedrooms for wall mounted panel heaters just in case, and have never needed to fit any.

 

Remember the noise of an ASHP is outside the house. Unless it is right under a window it won't bother you.  In comparison, the noise of a GSHP is in the house, so you better tuck it away from the living rooms or it is far more likely to annoy you,

[SteamyTea]

1 hour ago, ProDave said:

noise of a GSHP is in the house, so you better tuck it away from the living rooms or it is far more likely to annoy you,

As does a traditional boiler.

But on a new build you could fit both outside in a dedicated area.

Just remember that if fitting UFH on the ground floor, more insulation is best practice. Don't get trapped I to thinking building regs are really good enough. 

Edited February 13, 2020 by SteamyTea

[Dan1983]

Will bear this in mind, once I get a build quote through I will start sorting the finer details 

[Nickfromwales]

1 hour ago, Dan1983 said:

Will bear this in mind, once I get a build quote through I will start sorting the finer details 

Go for 100mm of EPS, then 100mm of PIR rigid foam type insulation above that. EPS is cheap as chips and will make a huge difference to the naff bit of PIR your BCO will ‘insist’ you install   

If you stay at home, then 100mm of screed will serve you well, as the thicker the slab, the more like a heat battery it will perform. 
Thin screeds need higher temps for longer durations, and the hysteresis is terrible in comparison to thicker ‘slabs’. Plus they don’t hold heat for very long either. They do heat up quicker, of course, but you only need to use a timer and learn how long it needs to come on for before affecting the room interior and vice versa. Eg with a thicker slab set it to come on sooner than you need, but also to turn off sooner as it’ll keep emitting heat until it cools off. 
It’s all dependant on what / how you’re building and how good it performs, so a bit tricky to call in a few posts. 

[SteamyTea]

2 hours ago, Nickfromwales said:

Thin screeds need higher temps for longer durations

Are you sure.

 

[Nickfromwales]

48 minutes ago, SteamyTea said:

Are you sure.

 

Yes, but it’s a coarse statement I agree. 
Just recounting every job I’ve been on with thin screeds vs the ones I’ve been on with thicker / more substantial heat density (?) / thermal inertia. 
Totally different jobs with hugely differing results.

Most of the issues are with managing the heat delivery to the manifold, and then getting it emitted from the slab ( screed ) in a comfortable and effective way. Lots of customers complained that it was either too hot or too cold as the over / undershoot was almost unmanageable.

Paper exercises are one thing, reality from practical experience is my church, so I can only recount what my actual experiences have been with the different disciplines.   

[SteamyTea]

1 hour ago, Nickfromwales said:

Lots of customers complained that it was either too hot or too cold as the over / undershoot was almost unmanageable.

To me that says that the delivery temperature is too high i.e. delivering too much energy in too short a space of time.

 

[Nickfromwales]

11 hours ago, SteamyTea said:

To me that says that the delivery temperature is too high i.e. delivering too much energy in too short a space of time.

 

Yes, but largely because ‘most’ generic types of heat source cannot deliver low enough amounts of heat in most situations. Therefore the heat on / heat off cycles aren’t sympathetic to short windows of heat injection. 
That is amplified by the emitter then mimicking those peaks and troughs. All comes together for a not-very-nice end result. 
Been to lots of property’s suffering from this, especially retrofit.

[scottishjohn]

6 minutes ago, Nickfromwales said:

Yes, but largely because ‘most’ generic types of heat source cannot deliver low enough amounts of heat in most situations. Therefore the heat on / heat off cycles aren’t sympathetic to short windows of heat injection. 
That is amplified by the emitter then mimicking those peaks and troughs. All comes together for a not-very-nice end result. 
Been to lots of property’s suffering from this, especially retrofit.

dare i say it --a good use for a themal mass to smooth things out

[Nickfromwales]

2 hours ago, scottishjohn said:

dare i say it --a good use for a themal mass to smooth things out

Dead man walking.......

[Jeremy Harris]

1 minute ago, Nickfromwales said:

Dead man walking.......

 

 

It's OK, I think we know he really means high heat capacity. . .

[Nickfromwales]

18 minutes ago, Jeremy Harris said:

 

 

It's OK, I think we know he really means high heat capacity. . .

Thermal inertia ?

[scottishjohn]

1 minute ago, Nickfromwales said:

Thermal inertia ?

or even thermal store

we all know what we mean 

[Nickfromwales]

Might get some T-shirts printed up.....?

[Ferdinand]

23 hours ago, Dan1983 said:

Cheers Dave,

i have just been having a read up, think I’m tempted to spec ASHP as seems easier to install plus advantage of being able to work in reverse.

guessing the newer systems are fairly quiet now compared to the older ones?

Bedrooms and lounge are going to be carpet so not sure if that effects the heat transfer of UFH? 

 

It does effect it, as does eg a bed on the ground vs one on legs.

 

I am planning to take my downstairs carpets *out* soon. ?

 

PS Thermal Mass is what Roman Catholics do near the Equator. Nothing to do with houses.

Edited February 14, 2020 by Ferdinand

[Jeremy Harris]

Heat capacity works reasonably well, as it determines how much sensible heat a given volume, or mass, of material will store for a given temperature differential.  Take our ground floor insulated slab as an example.  That has a volume of about 9m³ of concrete, and a mass of around 18 tonnes.  If that's heated to 2°C above room temperature then it can store about 36 MJ, or roughly 10kWh, of sensible heat that can be delivered (more or less) to the house. 

Edited February 14, 2020 by Jeremy Harris
Typos

[scottishjohn]

I had carpets to start with when Iretro fitted UFH --worked fine -but when i changed to tile floor it became more responsive --not sure i could see much difference in running costs

cos ihad underside of supended floor very well insulated 

[SteamyTea]

1 hour ago, Ferdinand said:

PS Thermal Mass is what Roman Catholics do near the Equator. Nothing to do with houses.

There was a TV programme in the 80s called Monkey.

There was a Dutch priest who frequently gave young village girls a blessing.

Turned out he was a German Nazi officer on the run.

Don't suppose they make kids programs like that anymore.

Edited February 14, 2020 by SteamyTea