Advice on space heating passive house

[dnoble]

We're in our second winter in an MBC timber frame house. 

5 bed, 4 kids. 240m2 approx

It has UFH pipes installed but I experimentally haven't connected them up. 

I think it's OK (with thermal longjohns etc ), but some of the less robust members of my house feel we need "proper" heating. 

It was 15 degrees inside this am (-2 outside overnight).

We do have a plug-in panel heater which will warm a single room quickly. 

We have a 9kW Sunamp unit which supplies hot water. This is mainly charged by solar PV. 

 

Question; 

Should we connect UFH to the Sunamp? Obv this will greatly increase drain on it and it'll need more topping up from the grid.

Is it worth getting an ASHP? I have left penetrations through the wall for one. 

If so would this heat the Sunamp more efficiently than grid, or can it directly connect to the UFH?

Or would it be most expedient just to get a couple of extra panel heaters on smart timers?

I'm reluctant to spend many Ks and get my head round yet more technology for the sake of a few degrees or saving a few quid. Is another big mental and financial outlay worthwhile (sorry for a rather subjective question)

Dan

 

 

 

[Conor]

Do you ever think you'll sell the house? Of yes, then stick in a small ASHP as you'll have have difficulties selling a house without central heating. I think we're a decade or two away from unheated passive houses being widely understood and accepted. 

 

 

[JFDIY]

15c is below the reccomended minimum for a workplace, I'm not surprised you're getting ear ache.

 

22c In my lounge and I've still got a jumper on.....

 

ASHP sounds a good investment, or a log burner for occasional boost in heat.

[PeterW]

31 minutes ago, dnoble said:

Should we connect UFH to the Sunamp?

You can’t - Sunamp is providing potable water not heating and there is no way to make it do both. 
 

31 minutes ago, dnoble said:

If so would this heat the Sunamp more efficiently than grid, or can it directly connect to the UFH?

Depends on the Sunamp but if it’s and electric only then there is no way to heat them with a water circuit and an ASHP doesn’t get hot enough to phase change the PCM (needs 59°C)

 

33 minutes ago, dnoble said:

Is it worth getting an ASHP? I have left penetrations through the wall for one. 

Yes - and they aren’t expensive. Do you have space for a buffer tank also where the UFH manifold is ..?

 

I would get a 3-5kW ASHP and connect it via a buffer and run off peak. Assuming you have PV diversion then also get a buffer that can take an immersion and connect this as second dump load to the PV. Also gives you redundancy in the event of failure of the ASHP. 

[Dan F]

You'll only need a small ASHP so shouldn't cost a huge amount, you can also use it to cool the house in the summer. Would be a shame to not use UFH given its installed. Panel heaters will never give you such a good even heat and temperature will more localized and osocilate a lot more.

 

It may not make sense to pay for a MCS/RHI install though, as payback will be low.  

 

Edited January 7, 2021 by Dan F

[ZacP]

What about a Willis heater connected UFH and to the solar panels somehow? If it’s only occasional heating, it might make more economical sense to have a lower initial outlay.

[dnoble]

6 hours ago, PeterW said:

You can’t - Sunamp is providing potable water not heating and there is no way to make it do both. 
 

Depends on the Sunamp but if it’s and electric only then there is no way to heat them with a water circuit and an ASHP doesn’t get hot enough to phase change the PCM (needs 59°C)

 

Yes - and they aren’t expensive. Do you have space for a buffer tank also where the UFH manifold is ..?

 

I would get a 3-5kW ASHP and connect it via a buffer and run off peak. Assuming you have PV diversion then also get a buffer that can take an immersion and connect this as second dump load to the PV. Also gives you redundancy in the event of failure of the ASHP. 

This is really useful advice and leads to more questions.

 

What size volume would the buffer tank need to be? I think there'd be room next to the UFH pipe manifold, There's a 1.5m wide under counter space potentially.

Can you recommend a small ASHP + tank?

 

DanF, How would the cooling in summer work? Do you send cold water round the UFH pipes or is it a direct function of the ASHP?

[Iceverge]

@dnoble

 

I'm watching this with interest as we haven't installed any heating in our passive house.

We're moving in soon and will play suck it and see with a panel heater or two. 

 

Have you tried running a plug in heater continually in a central area for a few days to boost the temperature of the contents and structure to something more comfortable.

 

Turning it on intermittently will only heat the air in the room, but it will return quickly to that of everything else around it once switched off. It takes a lot longer for walls ,furniture  etc to heat up than air. 

 

Did you do PHPP and if so what was your heating load?   

 

 

Edited January 7, 2021 by Iceverge
clarity

[Dan F]

1 hour ago, dnoble said:

DanF, How would the cooling in summer work? Do you send cold water round the UFH pipes or is it a direct function of the ASHP?

 

Yes, you send cold water around the UFH pipes. Cold enough to cool the slab but not too cold so as to cause condensation to form. The cold water comes from ASHP running in reverse, which most support.

[Gone West]

12 hours ago, Iceverge said:

I'm watching this with interest as we haven't installed any heating in our passive house.

We're moving in soon and will play suck it and see with a panel heater or two.

We heat our PH with three electric towel rails in the bathrooms and a small area of electric UFH in the kitchen. We have found that putting them on as soon as the house temperature starts to drop after the Autumn keeps the house at 23C without any problems. There is supplementary warm air heating from the MVHR if it's particularly cold for any length of time. We also have a solar gain area for Autumn and Spring heating. We are in the SE England near the coast and our wall and roof U values are 0.095 with airtightness of 0.47ACH. I ran a lot of iterations of PHPP before I was happy we would not need conventional central heating.

Edited January 8, 2021 by PeterStarck

[SteamyTea]

12 hours ago, Iceverge said:

Have you tried running a plug in heater continually in a central area for a few days to boost the temperature of the contents and structure to something more comfortable.

What I would do, and log the internal and external temperatures.

Then it is easy to work out properly what is needed.

 

The Range do some small, 400W, fan heaters with temperature and time controls on them.  About 10 quid each.

https://www.therange.co.uk/diy/heating/daewoo-digital-plugin-heater/#217528

[TonyT]

the initial post doesn't say what heating system is installed?

Is it gas  or oil?  If so and you are that hardy to live with 15 deg temps inside, fire up the boiler?

 

[SteamyTea]

3 minutes ago, TonyT said:

the initial post doesn't say what heating system is installed?

 

19 hours ago, dnoble said:

It has UFH pipes installed but I experimentally haven't connected them up. 

  

19 hours ago, dnoble said:

Is it worth getting an ASHP? I have left penetrations through the wall for one. 

 

Edited January 8, 2021 by SteamyTea

[TonyT]

Yes I knew he had UFH, but what was it connected to?

 

not connected them up could mean it’s not been done yet, not that there isn’t a boiler

[Pete]

32 minutes ago, PeterStarck said:

We heat our PH with three electric towel rails in the bathrooms and a small area of electric UFH in the kitchen. We have found that putting them on as soon as the house temperature starts to drop after the Autumn keeps the house at 23C without any problems. There is supplementary warm air heating from the MVHR if it's particularly cold for any length of time. We also have a solar gain area for Autumn and Spring heating. We are in the SE England near the coast and our wall and roof U values are 0.095 with airtightness of 0.47ACH. I ran a lot of iterations of PHPP before I was happy we would not need conventional central heating.

We have no heating upstairs but now and then it would be nice for some additional heating in the bathroom but as we have mvhr would this not be distributed throughout the house and not just warm the bathroom?

[Pete]

13 hours ago, Iceverge said:

@dnoble

 

I'm watching this with interest as we haven't installed any heating in our passive house.

We're moving in soon and will play suck it and see with a panel heater or two. 

 

Have you tried running a plug in heater continually in a central area for a few days to boost the temperature of the contents and structure to something more comfortable.

 

Turning it on intermittently will only heat the air in the room, but it will return quickly to that of everything else around it once switched off. It takes a lot longer for walls ,furniture  etc to heat up than air. 

 

Did you do PHPP and if so what was your heating load?   

 

 

We visited a Passive house before starting on our self build and on the day we went it was 19 degrees inside but felt cool so we decided to put ufh in our Passive house so we had a heat source

[Gone West]

2 minutes ago, Pete said:

We have no heating upstairs but now and then it would be nice for some additional heating in the bathroom but as we have mvhr would this not be distributed throughout the house and not just warm the bathroom?

We use the MVHR to distribute heat from the bathrooms, which are at around 24C, around the house as well as leaving doors open. Using the MVHR only works because it's a very small amount of heat required.

[dnoble]

1 hour ago, TonyT said:

the initial post doesn't say what heating system is installed?

Is it gas  or oil?  If so and you are that hardy to live with 15 deg temps inside, fire up the boiler?

 

There’s no heating system as it’s a passive house. I’m exploring the best way of supplementary heating via the UFH pipes I got installed as an insurance 

[TonyT]

Ah ok!

 

if it were me I would stick with  the fan heater, less grief 100% efficient, no servicing required.

 

or maybe a retro fit heater in the mhvr?

 

 

 

[dnoble]

On 07/01/2021 at 13:46, Dan F said:

It may not make sense to pay for a MCS/RHI install though, as payback will be low.

 

Can you explain this,  will it be much more expensive to install through a registered RHI company than DIY it?

 

If non RHI could a normally competent plumber (or even a minimally competent non-plumber-me) manage it?

[Bitpipe]

7 minutes ago, dnoble said:

 

Can you explain this,  will it be much more expensive to install through a registered RHI company than DIY it?

 

If non RHI could a normally competent plumber (or even a minimally competent non-plumber-me) manage it?

 

I think he means that RHI payments are contingent on how crap the house is currently performing. As you're passive and have a high SAP you won't get much if anything (the flip side of this is the number of existing houses getting ASHPs installed that prove totally inadequate for their needs).

 

I think a few here have DIYd their ASHP - if you have ducts and power etc then you are most of the way there. From what I've read on this site, the complexity is configuring it (i.e. the s/w)

 

If you just have empty UFH pipes though you will need a plumber to hook it up to a manifold, pump, controller etc. That's maybe a bit too involved for DIY.

[Dan F]

2 hours ago, Bitpipe said:

 

I think he means that RHI payments are contingent on how crap the house is currently performing. As you're passive and have a high SAP you won't get much if anything (the flip side of this is the number of existing houses getting ASHPs installed that prove totally inadequate for their needs).

 

I think a few here have DIYd their ASHP - if you have ducts and power etc then you are most of the way there. From what I've read on this site, the complexity is configuring it (i.e. the s/w)

 

If you just have empty UFH pipes though you will need a plumber to hook it up to a manifold, pump, controller etc. That's maybe a bit too involved for DIY.

 

Exactly.  Don't have personal experience as only got MCS-approved install quotes.  But from what other have said on the forum, you can either DIY or use a plumber that isn't MCS-approved and doesn't have the same overheads.  See:

 

[joe90]

If you don’t want the expense of an ASHP (but I think it’s a good idea) some here in passive houses use a Willis heater to give a small amount of heat into the slab via the UFH pipes you installed. It will give you an idea of what heat is required to get the house comfortable then you could consider an ASHP in the future if required. (I installed my own ?).

[dnoble]

I saw that Joe and wasn't sure what it meant, thanks for clarifying. Would you stll need a buffer tank or something? presumably you cant; just connect the mains to UFH pipes via a Willis heater?

Edited January 8, 2021 by dnoble
typo

[joe90]

@dnoble can’t remember who on this forum has done that but they will give you a better answer than me (but don’t think they used a buffer tank).       Anyone?