Heating/Cooling - best combo to go for?

[JohnMo]

1 hour ago, Iceverge said:

 

Was this because you had carpets? 

 

I think @Indy has wood and tiles. 

 

Fan cools run at about £300. I reckon it'd work out more expensive than UFH. 

 

 

Yes carpets. It's fine with harder floors, but with ufh being so slow you can bedrooms way to warm or  cool not really a happy medium. We just have just opted to have the bedrooms cool, open the door at 6pm, then it's fine for sleeping - not too hot or cold. We are long thin single storey so can two slightly different temps, from one end of the house to the other.

 

 

[Iceverge]

1 hour ago, G and J said:

So, the concept enshrined in 2) holds, the question is how much the screed would cool during the off period.

 

I have difficulty finding stuff on here, do you happen to know how to find that?

 

Fairly easy to calculate. 

 

All you need is the specific heat capacity of the screed to get a rough estimation. 

 

@TerryE has chapter and verse. However it was far down the line of perfections at the end of a very very low energy demand house. 

[Indy]

4 hours ago, JohnMo said:

Just looking at your drawings you have a lot of thermal bridging going on. Internal wall going straight to strip foundation. I would add a strip of thermolite (or similar) blocks to straddle the insulation. Same on the internal skin of outside walls. The first block of the internal skin do that in Thermolite.

To be fair, this is the document from the Structural Engineer and the architect hasn't yet finalised the drawings from his side. He's aware of my focus on airtightness and thermal bridging and my understanding is that there will be an updated set he produces alongside construction notes that should address some of these points?

 

I'm happy to take onboard points where taping etc needs to be done and swapping of blocks to more appropriate ones and this can be in the pack that we use the main contractor who will undertake the build. 

[Indy]

6 hours ago, Iceverge said:

 

Sorry for not picking this up earlier. The thread got a bit hijacked and I must have skipped it. 

 

 

Ok. I'll do my best, you'll have to widen the wall slightly but it'll save you thousand's and perform much better. 

 

1. Standard MVHR.

2. Monoblock ASHP to UFH ground floor only. Cooling if possible. 

3. UVC as you say is ok. Bigger is better. 

4. UFH on ground floor is good. 

5. I don't like fan coils. Unnecessary complexity in my opinion. Provide space  for A2A is easier in my opinion.

6. Don't know. 

7. No wet UFH upstairs just UFH electric under tiles. On ground floor bathrooms too. 

8. Include an electric spur for towel rads if you want them . ASHP runs too cold to do much with them.

9. Don't know. 

10. No thermostats in individual rooms.

Build well and the house will all be similar temp.

 

1. Standard MVHR.

Noted

 

2. Monoblock ASHP to UFH ground floor only. Cooling if possible. 

Noted

 

3. UVC as you say is ok. Bigger is better. 

Plan is 300L and 100L buffer tank is what I've been recommended. With 3 bathrooms and a cloakroom, we're on the verge of 300L being sufficient and we do tend to use a lot of hot water through the day with multiple showers.

 

4. UFH on ground floor is good. 

Noted

 

5. I don't like fan coils. Unnecessary complexity in my opinion. Provide space  for A2A is easier in my opinion.

This is the latest advice. A2A or split air con is what I had originally planned for. The discussion I've had with someone from an energy 'consultancy' who is putting together a full proposal for me is to go fan coils which will work out about 10k cheaper than air con. And the fan based radiators are 'as good as' internal air con and can get it down to fridge like temperatures.

 

6. Don't know. 

The question was to make sure that running ASHP in cooling mode wouldn't cause too many issues with condensation for the UFH embedded under the floor?

 

7. No wet UFH upstairs just UFH electric under tiles. On ground floor bathrooms too. 

Not sure on this one. We've gone back and forth a few times on this. The latest is that we have wet UFH in all the bathrooms on ground and first floor for sure. My wife likes to run the bedroom hotter than I like - at about 21-22C and is kinda insisting on having UFH.

If we were to increase the insultation in the floor and have the fan coil units in the bedrooms - would that negate the need for having the UFH? The cost for UFH is coming out to be about £7k per floor, so the £7k saved would mean we can easily fund the fan coil units with that saving (8 x £500ish).

 

8. Include an electric spur for towel rads if you want them . ASHP runs too cold to do much with them.

Yes, updated following advice on this thread

 

9. Don't know. 

Answered earlier in the thread, standard copper plumbing pipes.

 

10. No thermostats in individual rooms.

I really like the idea of being able to set the rooms at diff temps - but would this work with the setup we have?

I think the Fan coil units will have individual thermostats as well so this may be negated by having individual thermostats for each room.

[G and J]

31 minutes ago, Indy said:

 

1. Standard MVHR.

Noted

 

2. Monoblock ASHP to UFH ground floor only. Cooling if possible. 

Noted

 

3. UVC as you say is ok. Bigger is better. 

Plan is 300L and 100L buffer tank is what I've been recommended. With 3 bathrooms and a cloakroom, we're on the verge of 300L being sufficient and we do tend to use a lot of hot water through the day with multiple showers.

 

4. UFH on ground floor is good. 

Noted

 

5. I don't like fan coils. Unnecessary complexity in my opinion. Provide space  for A2A is easier in my opinion.

This is the latest advice. A2A or split air con is what I had originally planned for. The discussion I've had with someone from an energy 'consultancy' who is putting together a full proposal for me is to go fan coils which will work out about 10k cheaper than air con. And the fan based radiators are 'as good as' internal air con and can get it down to fridge like temperatures.

 

6. Don't know. 

The question was to make sure that running ASHP in cooling mode wouldn't cause too many issues with condensation for the UFH embedded under the floor?

 

7. No wet UFH upstairs just UFH electric under tiles. On ground floor bathrooms too. 

Not sure on this one. We've gone back and forth a few times on this. The latest is that we have wet UFH in all the bathrooms on ground and first floor for sure. My wife likes to run the bedroom hotter than I like - at about 21-22C and is kinda insisting on having UFH.

If we were to increase the insultation in the floor and have the fan coil units in the bedrooms - would that negate the need for having the UFH? The cost for UFH is coming out to be about £7k per floor, so the £7k saved would mean we can easily fund the fan coil units with that saving (8 x £500ish).

 

8. Include an electric spur for towel rads if you want them . ASHP runs too cold to do much with them.

Yes, updated following advice on this thread

 

9. Don't know. 

Answered earlier in the thread, standard copper plumbing pipes.

 

10. No thermostats in individual rooms.

I really like the idea of being able to set the rooms at diff temps - but would this work with the setup we have?

I think the Fan coil units will have individual thermostats as well so this may be negated by having individual thermostats for each room.

@Indy

 

Question: Have you ever lived in an airtight well insulated house?

[G and J]

2 hours ago, Iceverge said:

 

Fairly easy to calculate. 

 

All you need is the specific heat capacity of the screed to get a rough estimation. 

 

@TerryE has chapter and verse. However it was far down the line of perfections at the end of a very very low energy demand house. 

Indeed, I've been having a play....

 

 

OK, so I've some numbers, and gut feel says a 4C change in floor temp will feel f chilly - but what should I be aiming at?

 

The complicating factor for me is that on a -2.something day we will have the woodburner going, and maybe even on a 5C day.  But I'd like the system to work well on a normal cold day without a fire....

 

So what floor temp drop should I aim at?

[JohnMo]

14 minutes ago, Indy said:

3. UVC as you say is ok. Bigger is better. 

Plan is 300L and 100L buffer tank

You don't need a buffer with UFH, especially so on a single zone.

 

15 minutes ago, Indy said:

6. Don't know. 

The question was to make sure that running ASHP in cooling mode wouldn't cause too many issues with condensation for the UFH embedded under the floor?

UFH (cooling mode) will not have any condensation issues, as long as you keep flow temp sensible.

 

17 minutes ago, Indy said:

The cost for UFH is coming out to be about £7k per floor

Sorry that price is bonkers. Priced up the materials for mine the other day (192m2 worth) well less than £1k, took me on my own two days to install. You need 16mm Per-Al-Pert pipe, pipe clips and a manifold for each floor, you should be able to drive the whole lot from you heat pump, circulation pump. If you don't want to go to bother of balancing or paying someone to do it, install Salus Auto balancing actuators and connect so they are all powered all the time.

 

19 minutes ago, Indy said:

21-22C

Once you get well insulated and especially with UFH 22 deg starts to get uncomfortably hot - that's anywhere in the house. 

 

21 minutes ago, Indy said:

10. No thermostats in individual rooms.

I really like the idea of being able to set the rooms at diff temps - but would this work with the setup we have?

I think the Fan coil units will have individual thermostats as well so this may be negated by having individual thermostats for each room.

Fan coils alter output by varying the fan speed, they have a fixed throughput of water, so keeps the heat source happy. So not comparable with a normal UFH where the circuit is either on or off. We started with a thermostat in every room, it just made the system so expensive to run.  At the time we were on a boiler and its gas consumption was double what it should have been due to short cycling. Slowely removing the thermostats go us to calculated gas consumption. In the end we had one thermostat.

 

Have single wireless thermostat, so you can move once you move in to best location. Do not accept a thermostat that does not have a 0.1 deg hysteresis option. Computherm Q20RF are nice and do cooling and heating and drive multiple receivers if needed

27 minutes ago, Indy said:

fan coils which will work out about 10k cheaper than air con

Your certainly being taken for ride on pricing.

 

 

[Indy]

2 minutes ago, G and J said:

@Indy

 

Question: Have you ever lived in an airtight well insulated house?

Answer: Sort of yes. My first flat was a well built low rise new build, triple glazing and solid concrete floors. Had MVHR as well. 

 

Current house is a single brick (no cavity wall) 1930s semi with double glazing thats about 20 years old. I can actually feel the air blowing through when I hold my hand next to the bay windows. The only reason I haven't changed them is to preserve funds for the new build really. 

[G and J]

8 minutes ago, Indy said:

Answer: Sort of yes. My first flat was a well built low rise new build, triple glazing and solid concrete floors. Had MVHR as well. 

 

Current house is a single brick (no cavity wall) 1930s semi with double glazing thats about 20 years old. I can actually feel the air blowing through when I hold my hand next to the bay windows. The only reason I haven't changed them is to preserve funds for the new build really. 

Then you have an advantage over me as I haven’t and I’m struggling to imagine how it will feel.

[Indy]

5 minutes ago, G and J said:

Then you have an advantage over me as I haven’t and I’m struggling to imagine how it will feel.

Very warm, very quiet and did not need a lot of heating to come on - even during peak winters. We were on floor 3 (out of 4) so had heat coming from both the top and bottom which made it even better. 

[G and J]

5 minutes ago, Indy said:

Very warm, very quiet and did not need a lot of heating to come on - even during peak winters. We were on floor 3 (out of 4) so had heat coming from both the top and bottom which made it even better. 

We built ours in ‘91.  Better than the then building regs insulation but compared to our planned new pad it is a wind tunnel.  We are used to cool bedrooms and significant temperature variations during the day on cooler days.   Hence me asking so many stoopid questions….

 

How much will you be doing yourselves?

[Indy]

7 hours ago, Iceverge said:

The design appears to have bifold doors and a chimney still. 

 

My advice is to change these to a pair of french doors with fixed side lights and to get rid of the fireplace. 

 

You'll save thousands of pounds and the house will be far less drafty. 

 

 

They will be sliding doors and that cannot be changed. SWMBO has said so and that's the end of the matter.

 

The chimney was put in at the very early stages when we wanted a log burner, and I'm not sure anymore. However, I've been informed that we must build it to comply with the planning as it's part of the approved plans including the stack. Not sure what the alternative would be. 

[Indy]

7 hours ago, Iceverge said:

Another option is to include UFH on the first floor.for cooling mainly . What is it constructed from timber or concrete? 

 

 

As an aside do you have more drawings. The suggested roof methods may not be the best. 

Ground floor is beam and block floor.

First floor will be posi joist - 225mm deep.

[Indy]

31 minutes ago, JohnMo said:

You don't need a buffer with UFH, especially so on a single zone.

 

UFH (cooling mode) will not have any condensation issues, as long as you keep flow temp sensible.

 

Sorry that price is bonkers. Priced up the materials for mine the other day (192m2 worth) well less than £1k, took me on my own two days to install. You need 16mm Per-Al-Pert pipe, pipe clips and a manifold for each floor, you should be able to drive the whole lot from you heat pump, circulation pump. If you don't want to go to bother of balancing or paying someone to do it, install Salus Auto balancing actuators and connect so they are all powered all the time.

 

Once you get well insulated and especially with UFH 22 deg starts to get uncomfortably hot - that's anywhere in the house. 

 

Fan coils alter output by varying the fan speed, they have a fixed throughput of water, so keeps the heat source happy. So not comparable with a normal UFH where the circuit is either on or off. We started with a thermostat in every room, it just made the system so expensive to run.  At the time we were on a boiler and its gas consumption was double what it should have been due to short cycling. Slowely removing the thermostats go us to calculated gas consumption. In the end we had one thermostat.

 

Have single wireless thermostat, so you can move once you move in to best location. Do not accept a thermostat that does not have a 0.1 deg hysteresis option. Computherm Q20RF are nice and do cooling and heating and drive multiple receivers if needed

Your certainly being taken for ride on pricing.

 

 

 

Thanks, all valid points. I'm in the process of getting quotes and a lot of them come with the Surrey uplift applied. One quote we had for all the heating/cooling/PV/MVHR/UFH/basic automation was in the region of £80k! 

 

I'll be doing my own research and possibly getting the designs done separately and then get the builder to do it.

 

The answer to the other question is that I won't be doing too much myself - until the money runs out I guess! Young kids and a very hectic job means I'll have most of the work being done by a main contractor, though my plan is to do as much procurement as possible to find the best prices on things.

[G and J]

22 minutes ago, Indy said:

They will be sliding doors and that cannot be changed. SWMBO has said so and that's the end of the matter.

 

The chimney was put in at the very early stages when we wanted a log burner, and I'm not sure anymore. However, I've been informed that we must build it to comply with the planning as it's part of the approved plans including the stack. Not sure what the alternative would be. 

A variation of conditions.  In Suffolk it’s about £450 and takes 8 weeks.

 

But a woodburner is a beating heart….

[Iceverge]

At the risk of making @Indys life more complicated would you mind starting a new thread concentrating on the fabric as it's a slightly different issue than the heating/cooling and it might keep things a bit tidier. 

[Indy]

5 hours ago, Iceverge said:

At the risk of making @Indys life more complicated would you mind starting a new thread concentrating on the fabric as it's a slightly different issue than the heating/cooling and it might keep things a bit tidier. 

Taken your advice - separate thread started here 

 

[TerryE]

My last house was a circa 1700s stone farmhouse, concrete and tile ground floors. Extremely picturesque.  Lovely to live in -- in the summer; f'ing freezing in the winter unless I had two downstairs multi-fuel stoves on the go and the CH cranked up.  The exterior walls were typically cold (say ~10°C) to the touch.   My new self-build is passive class.   Jan and I were pretty anal about keeping U-Values to standard for class, and  tracking down then eliminating / decently mitigating bridging.  There were three bridging areas that crept into the build and that we addressed, but even so our house only performs at maybe 30% worse than the as-designed calcs -- but that's still 5× or more better than the typical new build. 

 

You have a huge insulation barrier internal to external in this class of house -- assuming that you haven't missed any bridging cock-ups in the build.  The internal floor-to-floor barriers are extremely small in comparison so everything everywhere is at or near room temperature to the touch.  We run our house as a single zone at around 22½°C though the CH algo only uses the cheapest Octopus half-hour slots so the temp does wobble around throughout the day by a degree or so.  We heat the GF with UFH in slab. We also have a couple of free-standing oil-filled rads that we use in winter for top up on the upper floors (also CH controlled), and we have a electric towel rad in the master bedroom en-suite; other than that there is no heating at all on the two top floors, just parasitic heat from the GF.   

 

I once went around the house one winter evening with a spot thermometer: the ground floors, ceilings, internal walls were within ½°C of the same temp.  The external walls about 1°C cooler and there was a cool hand's-width in the reveals around the external windows where there was some bridging through the timber framing of about 4-5°C but well above condensation thresholds and small in total W terms.  Ditto the first floor, but this was about 2°C cooler overall. (This was before we used the top-up rad.)  My son's bedsit is on the in-loft floor, but this is boosted by his games PC and two huge TV monitors. 🤣

 

So you can really run a passive-class house as a zone with GF-only heating.   Simple boosts work, and are extremely cost effective.  IMO, there is too much focus on getting run-rates to the absolute minimum, and not enough on overall through-life discounted costs.  In our case we have an electric-only resistively heated house.  This is still cheap to operate on an Agile tariff.  We built it ASHP-ready but have never made the investment case to install one as it would take maybe 15 years to get a payback.

Edited December 2 by TerryE

[Iceverge]

Similar route here. 

 

We have a block built passive class house. It's been running abour 17 kWh/m2 per year since we moved in. I was hoping for better but some of the bridging details around the windows etc aren't mega. During the build there was some things that you just give up on. 

 

We've just installed an A2A unit which has reduced our heating usage to about 1/3.  Prior to that we were just using a single plug in resistance heater.

 

In short if you make a very good job of the fabric you can forego a conventional central heating system. Its an approach I woudl only take if I was all over the airtightness and thermal bridging details however.