UFH and Outbuilding

[mandm65]

We got planning permission to build a 7mx7m outbuilding at the end of our garage.
The new outbuilding will primary be used for gym and cinema room but will have shower/toilet room.
As the new outbuilding will be independent from the main house (approx. 20M away) we are thinking best to put a new boiler (independent) to fulfil the heating/hot water requirements but unsure best to go combi or system?
Secondly, we also debating whether to have wet under floor heating or traditional radiators. We have wet UFH installed in the house so we are aware of the pros and cons of wet UFH but unsure wet UFH would be suitable for our occasional usage of the outbuilding?
Appreciate your input.
Cheers

 

[Agile]

I am surprised that you got permission for that with a toilet and shower. Because it creates a potentially separately occupiable dwelling most LA will not agree to them.

It all depends on how you will actually be using it. Many I see are rarely used during cold weather and for them an electric shower and electric heating would be more suitable.

If you are convinced you will really use it a lot in the winter then a combi boiler would be the best choice.

I would always use rads as they give a rapid heat up without premeditation. But in a new build wet UFH is not very expensive if you can wait for it to warm up. With that floor area it will consume up to 5 kW so a boiler with a large turn down ratio would be sensible to avoid short cycling.

Tony

 

[mandm65]

Thanks Tony, yes we are convinced that the usage will be heavy comes winter or summer.

The new build is adjacent to existing garage (double) so we are thinking to adding couple of rads to garage while the garage is also getting insulated/facelift as part of renovation.

As for the combi boiler with large turn down ratio, would you have any recommendation(s)?

Cheers

 

[Agile]

There is a Vokera with a turn down ratio of 10:1 and a Viessmann with 20:1.

I would use the boiler to directly supply the UFH at the appropriate 40-45 C flow temperature.

But with the cheaper Vokera, I would check with the manufacturer that they agree that it is suitable for running at such a low flow temperature.

Some other boilers may now have similarly high turn down ratios. A good installer should be able to advise you.

Tony

 

[muggles]

Sounds like a perfect job for a Viessmann 200-W B2KB to me. I personally wouldn't spec UFH in a room that is likely to be used spontaneously as it takes too long to react and warm up - rads are your best bet here for fast heat-up times. If you think you're able to plan your usage and it won't be spontaneous however, UFH would be a good option.

 

[mandm65]

Thanks Andrew, yes i am hoping to utilise the new technology (remote/net controls) so its encouraging to know that wet UFH could be an option, we are looking at wet room for the shower so UFH would be ideal.

Any recommendations for (49M2 coverage) wet UFH system combined with remote/net controls?

 

[Agile]

We have wet UFH installed in the house so we are aware of the pros and cons of wet UFH but unsure wet UFH would be suitable for our occasional usage of the outbuilding?
Appreciate your input.

Cheers

Well you will be aware that UFH needs about two hours to get the room up to temperature in cooler weather.

I would never have UFH in a room like that as I am too mean to leave heating on unless I was absolutely sure that I was going to use it every time.

Instead I would use rads and know that it would only be 20 mins to get it hot.

There is another drawback to UFH. That is the cool down time. If I was seriously exercising in a gym then I would want it to be much cooler and with rads could achieve that pretty quickly! The alternative is to open windows/doors and waste the heat.

Tony

 

[mandm65]

Thanks Tony i appreciate what you are getting at, slightly off topic but still relevant.

Does the expert think the heat pumps (air/ground) is matured technology to be considered cost effective option for firing the UFH?

 

[muggles]

Thanks Andrew, yes i am hoping to utilise the new technology (remote/net controls) so its encouraging to know that wet UFH could be an option, we are looking at wet room for the shower so UFH would be ideal.

Any recommendations for (49M2 coverage) wet UFH system combined with remote/net controls?

If you go for the Viessmann then they do some fantastic controls of their own, well matched to the boiler for best efficiency and Internet enabled. Are you wanting more than one zone in your outbuilding (IE do you want to be able to heat the bathroom to a different temperature/at different times to the cinema/gym (which I assume are the same room??)

Thanks Tony i appreciate what you are getting at, slightly off topic but still relevant.

Does the expert think the heat pumps (air/ground) is matured technology to be considered cost effective option for firing the UFH?

Air source is more expensive to run when it's colder outside, IE when you need it most. I'm personally not a fan. Ground source works very well but is very expensive

 

[mandm65]

Yes Andrew i guess 49M2 would have to be divided in to multiple zones, i am looking to achieve max efficiency.
Great, i will pay more attention to Ground source, i have the space (20M), assume there is enough evidence out there which justify the spend?

 

[Agile]

Heat pump will always be more expensive than gas.

You talk about wanting efficiency. But then you seem to want to heat it most of the time whether occupied or not.

UFH has to be on for a minimum of two hours!

Rads can heat the room in 20 minutes so can be used for short periods.

I would never see any benefit in multiple zones in one single area. As for a bathroom on a separate zone, madness!

Tony

 

[mandm65]

Tony you have not given up on traditional rads, i guess evidence here suggest that we go back to the drawing board and look at the feasibility of UFH once again.
Surprise by the fact that 'Heat pump will always be more expensive than gas', i guess like many things, this is also a hype!
I let more knowledgeable (Andrew) comment re bathroom on a separate zone.

 

[muggles]

Ground source heat pumps are great if your primary objective is to be environmentally friendly, but if you're looking for the cheapest whole-life cost then a decent gas boiler will knock the socks off GSHP unless you manage to get a significant grant. If you're going for the pipe-in-trench method, as a rough rule of thumb you need about four times the area of land to the area you're trying to heat, so in your case you'd need about 200m². This does depend on local site conditions, however. Boreholes take up much less room, but you can be looking to drill anything up to 150m down, and at approx £80 per metre of drilling you'll soon ruin your bank balance.

Back to the real world, I'd say the bathroom on a separate zone is the best plan - you'll always want it to be warmer in there than in the gym/cinema room (still assuming this is the same room as you haven't contradicted me...I'll call it the gymcin), but equally you'll no doubt want the gymcin to be warmer when you're watching a movie than when you're working out. It could be made to work so that the bathroom is warmer than the gymcin without having two zones by simply having more UFH pipe per m² in that area, but you wouldn't have any control over the difference in temperature between the two, so two zones are required for best control

 

[mandm65]

Thanks Andrew, i guess the GSHP is out of the equation on both front, available area of land/cost.
Yes agree with your logic, it certainy make sense to have more UFH pipe per m² in the bathroom.
I am now leaning towards the traditional rads, yes change of heart here , considering we needed to put the rads in the garage.
Now do you guys still recomend that i go for Viessmann 200-W B2KB for traditional CH system or there is a better option?
For the shower/wetroom, would we need shower pump to gain sufficent pressure or normal shower would be fine?
Cheers

 

[Agile]

The viessmann 200 is a very good boiler.

A combi uses mains water and so gives mains pressure hot water.

You don't need, and cannot use, a shower pump with a combi.

It is possible to use both conventional rads ( for rapid heat up ) as well as UFH for the more even heat distribution.

In that case the TRVs on the rads turn off when the room is mostly up to temp and heat is then supplied an hour or so later when the UFH has warmed up the floor slab.

On a new build that is not as much extra as you might imagine.

Tony