Advice on heating options for new build, esp bathrooms

[Norbert]

We have recently got PP for demolition and rebuild, so now getting into detailed planning. House fabric and technology will be  to a high standard  (U .11 or .14 all around), good airtightness, MVHR, ASHP for  UFH and DHW, PV on roof, battery etc.

 

I have completed Jeremy Harris's spreadsheet which indicates that a 5kw ASHP will be all that is needed, even over sized. I understand that open loop, minimal or no zoning and weather compensation is the most efficient way of running it.

 

The house will have upstairs lounge, study, bedroom and bathroom. Downstairs kitchen/dining.family, bedroom with en-suite, WC and plant room.

 

We recently had the opportunity to live in a friends PH while they were on holiday which was very useful. We had the main open plan kitchen/diner/lounge at a constant 20C. All other doors kept closed, bedrooms and bathrooms settled at 16C (perhaps a bigger difference than I expected), that suited us, we do not like hot bedrooms.

 

So to our future house, I would like some advice on heating options. Given that the lounge is upstairs I feel that we cannot rely on UFH downstairs for that. So options are UFH upstairs in lounge and perhaps study as well, OR second A2A heat pump that would supply heat on demand and could also do cooling in summer using surplus PV.

 

Then to bathrooms. I think 16C in a bathroom is perfectly OK for most of the time. It seems overkill to have UFH and 20C all the time. What would be useful would be to have the ability to add extra heat as needed for shortish periods, either manual or timed. This would need to be responsive which UFH would not be. Options would appear to be:

• Electric towel rads on a cut out timer, put on say 1hr in advance
• Towel rads driven by ASHP (but would that need a higher temp than the UFH?, could that be driven by the DHW temp of 45/50?)
• Electric wall panel heater, perhaps IR delivering instant heat

 

any other options to consider?

[Kelvin]

We don’t have any heating upstairs for the two rooms. We wired for fitting panel heaters in case we ever needed to actively heat the rooms. The upstairs bathroom is heated by an electric towel radiator. The house isn’t finished yet so it’s hard to say how it will work but it seems to be working ok so far. 

[Dave Jones]

we have gone for elec towel rads all controlled by a timer from plant room. the solar diverter can turn them on as well should the hot water tank be upto temp and there is spare solar available.

[Nic]

1 hour ago, Norbert said:

We have recently got PP for demolition and rebuild, so now getting into detailed planning. House fabric and technology will be  to a high standard  (U .11 or .14 all around), good airtightness, MVHR, ASHP for  UFH and DHW, PV on roof, battery etc.

 

I have completed Jeremy Harris's spreadsheet which indicates that a 5kw ASHP will be all that is needed, even over sized. I understand that open loop, minimal or no zoning and weather compensation is the most efficient way of running it.

 

The house will have upstairs lounge, study, bedroom and bathroom. Downstairs kitchen/dining.family, bedroom with en-suite, WC and plant room.

 

We recently had the opportunity to live in a friends PH while they were on holiday which was very useful. We had the main open plan kitchen/diner/lounge at a constant 20C. All other doors kept closed, bedrooms and bathrooms settled at 16C (perhaps a bigger difference than I expected), that suited us, we do not like hot bedrooms.

 

So to our future house, I would like some advice on heating options. Given that the lounge is upstairs I feel that we cannot rely on UFH downstairs for that. So options are UFH upstairs in lounge and perhaps study as well, OR second A2A heat pump that would supply heat on demand and could also do cooling in summer using surplus PV.

 

Then to bathrooms. I think 16C in a bathroom is perfectly OK for most of the time. It seems overkill to have UFH and 20C all the time. What would be useful would be to have the ability to add extra heat as needed for shortish periods, either manual or timed. This would need to be responsive which UFH would not be. Options would appear to be:

• Electric towel rads on a cut out timer, put on say 1hr in advance
• Towel rads driven by ASHP (but would that need a higher temp than the UFH?, could that be driven by the DHW temp of 45/50?)
• Electric wall panel heater, perhaps IR delivering instant heat

 

any other options to consider?

Hi can you post a link to the spreadsheet please

 

[Norbert]

My spreadsheet attached. The first sheet is my dimensions to put into the spreadsheet

Heat loss calculator.ods

[JohnMo]

1 hour ago, Norbert said:

open loop, minimal or no zoning and weather compensation is the most efficient way of running it.

 

After quite awhile messing with WC, I actually find it cheaper to run a set flow temp of 35, and let it run as long or short as required by a 0.1 hysterisis thermostat. Low heating demand and WC doesn't make that much difference, my curve was something like 0.3 per Deg OAT starting at 10 degs down to -5. I get a consistent CoP of just over 3, but only because I make it heat during the night when it's coldest - because my tariff is cheapest then.

 

Bathroom towel rails, we did electric. If you do UFH in bathrooms cram as much pipe into the floor as can, as floor surface area ends up quite small. If you want to do intermittent bathroom heating the output needs to quite a bit higher than you think you need. Especially if the ensuite if attached to bedroom at 16 to 18 Deg.

[ToughButterCup]

2 hours ago, Norbert said:

• Electric towel rads on a cut out timer, put on say 1hr in advance
• Towel rads driven by ASHP (but would that need a higher temp than the UFH?, could that be driven by the DHW temp of 45/50?)
• Electric wall panel heater, perhaps IR delivering instant heat

 

A small super cheap electric underfloor heating element, and an electric towel rail, both on a timer.

For two bathrooms,

• underfloor electric mats were £50 each (Wickes end-of-line-sale) ,
• heated rails £350 and £400 (the more expensive one fits in a corner),
• Thermostat not needed (on full for two hours at a time - or an additional two hours boost)
• Timer £45,
• sparky fitted and tested £86.
• Be sure to buy a continuous  circuit tester if you are laying tiles over the underfloor mat. (£10)

 

Two bathrooms £1000. SWMBO loves the fitting in her bathroom. 

[SteamyTea]

8 hours ago, Norbert said:

second A2A heat pump that would supply heat on demand and could also do cooling in summer using surplus PV.

That could work quite well.

Can it be incorporated into, what would in effect be, a forced air heating system, or oversized MVHR ducts?

If your house is upside down, and you have loft space, then fitting ducts with 2 or 3 times the normal diameter should be easy.

[PNAmble]

We are building an upside down house , 0.11 insulation, pre board airtighness test is 0.42 (planned 0.6).  5kw heat pump, 300l DHW tank.  We’ve gone Radiators.  Upstairs and downstairs.  Small ones.  Plan is to run at 35/30 at -3.     
 

works for us as master bed is also upstairs, north facing downstairs 3 bedrooms (210m2 in total).  UFH to me is good if you have a slab to heat where you ‘live’ but in our case it would have been a waste of money 

Edited March 3 by PNAmble