Advice gratefully received for the heating and energy creating and storage in our SIP

[Louise B]

I'd be grateful for some fairly base level advice please. 

 

We're building a four bedroom, three bathroom SIP house, close to the sea in Berwickshire. It faces NE as the sea views are amazing. 

 

How to heat the house and water and how to potentially create and store energy feels like an overwhelming subject.

 

We won't use the house all the time until our kids have left school in 7 years time. We visited a similar house on the West coast of Scotland a few years ago and they said that they regret putting down a tiled floor as they hardly ever turn on their ASHP. It was 19 degrees in March and they hadn't\t been there for 2 months. That made us think that potentially you spend a lot of money on things you hardly ever use and that doesn't feel sensible. 

 

We'll definitely have a MVHR and a wood burning stove. We have a large garden and space for ground mounted solar. 

 

I guess we want a simple system that is tried and tested and good value. We'd be very grateful for your experience. 

 

Thanks so much

 

 

[SteamyTea]

20 minutes ago, Louise B said:

It faces NE

Not very good for PV generation.

Also, if you have larger windows that side of the house, the heat losses will be greater.

 

My house, though terraced, is NE-SW, the rear (NE) is always cooler.

 

As for the theory behind energy, that is really simple.  You have energy, which is the amount of fuel in the tank, and power, how fast you use that tank full.

The unit of energy is the joule (J), and 3,600,000 J is a kWh (what you pay for, or store).

Power is the watt, (W) and is a J/s (J.s^-1).  As it is a watt is a small unit, we tend to use the kilowatt, 1000 watts (kW).

Temperature should really be the kelvin (K) scale, but we tend to use celsius (°C).  There are times when it does matter when doing the sums.

Temperature is not energy.  I shall repeat that, temperature is not energy.

Mass is the kilogram (kg).

Distance is the metre (m).

Time is the second (s).

Energy goes from a higher state to a lower state, unless mechanically moved.  So flows naturally from hot to cold.

There is no magic in thermodynamics, it is all well understood.

 

You may notice that I have spelt watt and joule with lower case first letters, this is to stop confusion with the people they are named after, Watt and Joule.  The unit initial though is a capital.

Just to make it worse, prefixes are generally lower case, until they get large, so k for kilo (1000) but M for mega (1000000).

Some people think it is a bit pedantic and anal fussing about units, but it saves confusion.

 

Just reread your post.  You may require planning permission for a PV system that is ground mounted (>9m² from memory).

Wood burning stoves are a huge particulate pollution source.  Best to avoid them.

Edited February 10 by SteamyTea

[Benpointer]

2 hours ago, Louise B said:

It faces NE

 

1 hour ago, SteamyTea said:

Not very good for PV generation.

 Although most houses have at least two sides, so if the other one faces south west, that'd be good for PV.

 

Regarding the friends who 'regret their tiled floor because they hardly ever put their ASHP on', they are confusing things a bit.  Presumably they had the tiled floor because they had underfloor heating and they had UFH because they had an ASHP.  But none of those links are compulsory: you could put in a wooden floor over UFH and you could run UFH without an ASHP (though that would be an odd choice today).

 

If you are only using the house for short periods the woodburner may be sufficient if the insulation levels are very good - your SAP calculation should help you decide that.  But in any event at build time it would be sensible to put UFH pipes in when the floor is laid if there is any chance you might need more heating than the woodburner at some future stage.

[Alan Ambrose]

At the risk of being controversial - woodburners & gas boilers are good for heating up a place quick. Heat pumps and UFH are good at being on for long periods and heating things up slowly but being more ecological.

[Marvin]

1 hour ago, Alan Ambrose said:

At the risk of being controversial - woodburners & gas boilers are good for heating up a place quick. Heat pumps and UFH are good at being on for long periods and heating things up slowly but being more ecological.

Nothing controversial with that!

 

We work around the problem of being cold when we first arrive by putting an electric heater on for a while. Also with home automation systems I think you could probably heat the home up using your phone to control it.

 

If your home is going to use very little energy to heat up in the winter then it might become quite hot in the summer. Best to start with the SAP calculations in my opinion.

 

As @Benpointer comments, its probably best to build as if you are going to live full time in it because then in the future you could, or in the future some other people could. 

 

[SteamyTea]

48 minutes ago, Marvin said:

If your home is going to use very little energy to heat up in the winter then it might become quite hot in the summer.

If the building regulations are properly applied, then that is not a problem.

[Marvin]

8 minutes ago, SteamyTea said:

If the building regulations are properly applied, then that is not a problem.

So no chance of any problems there then....

[Nickfromwales]

Fitting an ASHP for UFH and DHW (domestic hot water) is an absolute no brainer. 
 

If the house is going to be built airtight (sub 1.0ACH minimum) and MVHR is included in the overall M&E spec, then the heating requirements should be very low anyways. ASHP + UFH with cooling via the ground floor slab must be considered for full time occupation of the dwelling   To not do this now will come back and bite you on the ar@e I assure you. 

 

Very likely the WBS will be lit a few times and you’ll then soon become overwhelmed by the amount of localised heat from it, the biggest issue being it’ll be a well insulated and airtight house; MVHR will not move the heat out of the room as fast as it’s being produced, so hopefully nobody has suggested it would ‘distribute’ heat through the home.

 

For the times the dwelling is unoccupied the system will just mothball itself. You’d set the room stat to say 17°C, for eg, and unless the house gets that cold the heating won’t come on. Same for DHW, it’ll just do an automatic anti-legionnaire purge every 7 days.

 

If there’s PV (ground mounted can be facing due south(?) or East/ West split) then you’ll very likely have no associated running costs when unoccupied (when calculated over the year). Better again if there’s a battery, but I’d probably not bother with that until the 7 years are up. Just set the purge to happen at midday and let the PV cover that.

 

Have you calculated the cooling requirements, for when the house is used routinely and you get a series of very hot days back to back? Part O compliance etc.

 

If you have an ASHP that can cool you can then practically remove a lot of that problem heat, whereas without it you’d be left with manually purging the property; achieved by strategically opening doors and windows which would be more of a PITA than you think. It would need to be done all the way from very early morning until into the late evenings, EVERY SINGLE DAY, and if the outside temp is high the cooling effect is minimal at best. Personally I hate being over 21°C, and at 22+ I want to kill.
 

Do not compare doing this in a current, draughty, poor standard house vs this new house, as they’ll be chalk and cheese. Very different world that you’re stepping into, but very nice when designed, and thought out properly. 

 

You say you don’t want to spend money on something you say you’ll “hardly ever use”, and I think that statement is based on naivety, sorry, and would be the worst decision you make. 
 

A tiled floor that is unheated will definitely feel colder under bare feet, but that’s simple to avoid with wood or LVT, but in honesty if you’re in a house of this type and the UFH is on, your (tiled) floors would not feel ‘heated’ to the touch; your skin / body temp would not be far enough away from the surface temp to make this notable.

 

To achieve a room temp of 21°C (which is very warm in this type of house) would require a floor temp of possibly 24/25° (max, in depth of winter) but likely less when considering occupants, appliances and solar gains etc.

 

The ASHP would barely be doing much at all to provide that background heat, and for most of the year you’d be doing PV > DHW for next to nothing and setting it to heat off cheap rate overnight during winter.

 

The ASHP can also be used to send heated or cooked water to the ventilation (MVHR) to further improve things, which adds a bit more ‘climate control’ or to a fan coil unit for bulk localised cooling (hall / stairs / landing etc). Lots of options but each situation is feasibly unique, yours inclusive as it’s N/E facing and you’re coastal.

 

All this will absolutely “be used” so I think you need a rethink    
 

Members on here have built to passivhaus standards and beyond, and still report needing at least some heating during winter quote “to avoid divorce”, but most have either designed in cooling (via slab & UFH or with fan-coil units) or were forced to retrospectively install an A2A system (air con) for the summers.

 

Simple’s, eh?  

[Nickfromwales]

45 minutes ago, SteamyTea said:

If the building regulations are properly applied, then that is not a problem.

I disagree completely. 
 

B Regs are bad on a good day, if you work to them then prepare to fail.

 

36 minutes ago, Marvin said:

So no chance of any problems there then....

lol.

[SteamyTea]

1 hour ago, Nickfromwales said:

1 hour ago, SteamyTea said:

If the building regulations are properly applied, then that is not a problem.

I disagree completely. 

So you saying that the industry standard Part O is a work of fiction?

[Marvin]

1 hour ago, Nickfromwales said:

Have you calculated the cooling requirements, for when the house is used routinely and you get a series of very hot days back to back? Part O compliance etc.

 I don't think I want windows to open, when no one is at home, to ventilate the building so the building would need Air to Air systems.(As I understand it). Holding the heat in causes all the building contents to absorb the heat and because of the thermal resistance of the building once in it will take as long to cool as to heat (without intervention).

 

Looking forward to our changing environment, with what appears to be more extreme events, I think that buildings for the soon to be environment need to be built tougher and more resistant to changes than covered in the building regulations.. Building design improvements take years to develop into regulations so they are always behind the buildings life time requirements. Calculating our building heating requirement I assumed a low point of -8 Celsius. Not enough attention was paid to overheating which I'm trying to deal with.

 

A forever home need to cope with the future demands.... assuming we're still here.

 

Good luck

 

M

 

 

 

[Nickfromwales]

52 minutes ago, SteamyTea said:

So you saying that the industry standard Part O is a work of fiction?

I'm saying it absolutely doesn't factor sufficiently for each individual circumstance, it's a blanket policy at best.

 

Building regs are, and will likely always be, the worst standard you can legally build to.

[Nickfromwales]

11 minutes ago, Marvin said:

I don't think I want windows to open, when no one is at home, to ventilate the building 

My point was more about the inconvenience of all this when the house IS occupied, eg having to open bedroom doors and windows etc when someone is snoozing on a Saturday morning for eg.

 

It's just something I dislike, even in PHPP; one example is where I just agreed a new approach with a PH certified architect & (our) client after he had already proposed an M&E solution directly to, without my knowledge, and then I objected due to many of the inconsideration's it assumed the clients would 'live with'.

 

These contained many days of the year where the dwelling would routinely achieve internal temps at >25^oC (an infinity symbol was conveniently inserted in that box iirc) and would require E/W purge 'cross-ventilation' pathways from ground floor to 1st floor....tidy.....and many other days where auxiliary heating would be required during the winter (eventual admission was that the client would have to roll out oil filled rads and moderate their output per room / space to prevent overheating!). Joy!

 

It's only when you get someone who knows these things inside and out, form all perspectives, do you seem to ever stand a chance of "getting it right", especially as a layman or novice self builder. I've often become quite fed up of babysitting 'qualified' people when working for many self build clients over the years who say they "do this as part of their day-to-day routine", but soon are demonstrating comprehensively, just how incomprehensive their approach actually is. Sometimes it's just downright scary how highly regarded these people become, with not very much good reason.

 

Each instance requires a fresh approach, so it's difficult to pin a tail on any one donkey here, but happy to provide answers to any specific questions, if that's of help .

 

35 minutes ago, Marvin said:

so the building would need Air to Air systems.(As I understand it).

Not necessarily. I objected, as above, and presented a new MVHR / heating / cooling strategy, and subsequently got an outcome 1% higher in efficiency than the PH certified architect (which is a big amount apparently). That was just from asking proper questions of the client(s) and knowing how to best provide practical solutions to create a comfortable home for someone to practically live in it. All to often the focus is on the pinnacle of a dwelling in the eyes of the designer, with little regard for the people who may then be trapped inside...  

[Marvin]

3 minutes ago, Nickfromwales said:

My point was more about the inconvenience of all this when the house IS occupied, eg having to open bedroom doors and windows etc when someone is snoozing on a Saturday morning for eg.

 

Its also pretty inconvenient if some one climbs in through an open window and robs you when arguing with your insurance company.😂 

[Nickfromwales]

2 minutes ago, Marvin said:

Its also pretty inconvenient if some one climbs in through an open window and robs you when arguing with your insurance company.😂 

I thought I'd stage the delivery of all the negatives, lol. You know, just allow them time to have a cup of tea and a Valium in between etc.

[joth]

51 minutes ago, Marvin said:

Its also pretty inconvenient if some one climbs in through an open window and robs you when arguing with your insurance company.😂 

 

This is largely mitigated by having an automatic opening on the highest windows, ideally over a vaulted hallway/landing, somewhere not easily accessible but injects cool air right to centre core of building. Skylights work well, but "celestial windows" seem ideal that I've set this up with in one property: vertical orientation means safe to open even when raining, and chain-motor limit means very narrow space to climb through and then a 30' drop on the inside -- by the time some dude is motivated to climb in through that, they're going to find their way into your (remote, unoccupied) property whatever you do.

 

More practically, the stages for unoccupied overheating should be to first put the MVHR on bypass, then on boost, and only then open said windows.  

[Marvin]

7 minutes ago, joth said:

 

This is largely mitigated by having an automatic opening on the highest windows, ideally over a vaulted hallway/landing, somewhere not easily accessible but injects cool air right to centre core of building. Skylights work well, but "celestial windows" seem ideal that I've set this up with in one property: vertical orientation means safe to open even when raining, and chain-motor limit means very narrow space to climb through and then a 30' drop on the inside -- by the time some dude is motivated to climb in through that, they're going to find their way into your (remote, unoccupied) property whatever you do.

 

More practically, the stages for unoccupied overheating should be to first put the MVHR on bypass, then on boost, and only then open said windows.  

Live in a bungalow.

[Nickfromwales]

57 minutes ago, joth said:

and then a 30' drop on the inside

How big is your chuffing house?   

 

Are you willing to adopt? 

[joth]

3 hours ago, Nickfromwales said:

How big is your chuffing house?   

 

Are you willing to adopt? 

Not my house! Just one I installed Loxone into

Yeah the sparky was not chuffed when they had to get the tower up there to fix the window motor wiring 😂

 

[Louise B]

8 hours ago, Nickfromwales said:

Fitting an ASHP for UFH and DHW (domestic hot water) is an absolute no brainer. 
 

If the house is going to be built airtight (sub 1.0ACH minimum) and MVHR is included in the overall M&E spec, then the heating requirements should be very low anyways. ASHP + UFH with cooling via the ground floor slab must be considered for full time occupation of the dwelling   To not do this now will come back and bite you on the ar@e I assure you. 

 

Very likely the WBS will be lit a few times and you’ll then soon become overwhelmed by the amount of localised heat from it, the biggest issue being it’ll be a well insulated and airtight house; MVHR will not move the heat out of the room as fast as it’s being produced, so hopefully nobody has suggested it would ‘distribute’ heat through the home.

 

For the times the dwelling is unoccupied the system will just mothball itself. You’d set the room stat to say 17°C, for eg, and unless the house gets that cold the heating won’t come on. Same for DHW, it’ll just do an automatic anti-legionnaire purge every 7 days.

 

If there’s PV (ground mounted can be facing due south(?) or East/ West split) then you’ll very likely have no associated running costs when unoccupied (when calculated over the year). Better again if there’s a battery, but I’d probably not bother with that until the 7 years are up. Just set the purge to happen at midday and let the PV cover that.

 

Have you calculated the cooling requirements, for when the house is used routinely and you get a series of very hot days back to back? Part O compliance etc.

 

If you have an ASHP that can cool you can then practically remove a lot of that problem heat, whereas without it you’d be left with manually purging the property; achieved by strategically opening doors and windows which would be more of a PITA than you think. It would need to be done all the way from very early morning until into the late evenings, EVERY SINGLE DAY, and if the outside temp is high the cooling effect is minimal at best. Personally I hate being over 21°C, and at 22+ I want to kill.
 

Do not compare doing this in a current, draughty, poor standard house vs this new house, as they’ll be chalk and cheese. Very different world that you’re stepping into, but very nice when designed, and thought out properly. 

 

You say you don’t want to spend money on something you say you’ll “hardly ever use”, and I think that statement is based on naivety, sorry, and would be the worst decision you make. 
 

A tiled floor that is unheated will definitely feel colder under bare feet, but that’s simple to avoid with wood or LVT, but in honesty if you’re in a house of this type and the UFH is on, your (tiled) floors would not feel ‘heated’ to the touch; your skin / body temp would not be far enough away from the surface temp to make this notable.

 

To achieve a room temp of 21°C (which is very warm in this type of house) would require a floor temp of possibly 24/25° (max, in depth of winter) but likely less when considering occupants, appliances and solar gains etc.

 

The ASHP would barely be doing much at all to provide that background heat, and for most of the year you’d be doing PV > DHW for next to nothing and setting it to heat off cheap rate overnight during winter.

 

The ASHP can also be used to send heated or cooked water to the ventilation (MVHR) to further improve things, which adds a bit more ‘climate control’ or to a fan coil unit for bulk localised cooling (hall / stairs / landing etc). Lots of options but each situation is feasibly unique, yours inclusive as it’s N/E facing and you’re coastal.

 

All this will absolutely “be used” so I think you need a rethink    
 

Members on here have built to passivhaus standards and beyond, and still report needing at least some heating during winter quote “to avoid divorce”, but most have either designed in cooling (via slab & UFH or with fan-coil units) or were forced to retrospectively install an A2A system (air con) for the summers.

 

Simple’s, eh?  

Thank you so much. That was absolutely the answer I hoped for. So helpful and practical. Thank you so much for taking the time. Louise

[Nickfromwales]

2 minutes ago, Louise B said:

Thank you so much. That was absolutely the answer I hoped for. So helpful and practical. Thank you so much for taking the time. Louise

I have been quoted to have “no varnish” lol, so those are just my nuts & bolts opinions, but these come from having done a large number of successful M&E projects for self builders, and having kicked a good few ‘associated professionals’ arses into shape along the way.

 

Another day in the office 🫡😁