NEWBIE eco self build

[Bitpipe]

1 hour ago, ukjamie said:

I would love to achieve A rating! We have a great architect who does these designs/builds on a regular basis, so with his guidance we should gain a good rating. being a timber framed building should help wih the solar gain, but I am not 100% sure of all of this yet. Might have to get some of those old cloth snakes by the back door!

 

Solar gain is usually a function of how much glass you have, the orientation and external shading. The frame fabric can help but usually requires a high decrement delay type insulation like blown cellulose.

 

Once a moderately well insulated building overheats due to to much solar gain through the windows, it is difficult to cool it down, so effective shading is really important - be that trees, bris soleil, external shutters or reflective film/glass. Overheating can happen year round, not just in summer and is actually more prevalent in spring and autumn when the sun is lower in the sky and can penetrate deeper into the house. A stack ventilation strategy (e.g. high level velux) can help flush the house with cool air at night and good airtightness will keep that cool air in the house for the following day. MVHR will keep air fresh and humidity low.

 

Also be aware that air tightness is the responsibility of all trades - great the the frame company seem to commit to it but this needs to extend to the window fitters and any trade that penetrates the envelope, like electricians or plumbers. All penetrations need to be taped and sealed, one careless trade can render the whole airtightness void. Your blower test will show the result but it can be hard to rectify issues if the house is largely complete and the problems are hidden.

 

As Nick says, MVHR is a must if your house is anyway airtight otherwise you will have no fresh air without trickle vents in windows and then all your precious heat is freely leaving the house which will drive up running costs. MVHR does not mean you can't open doors & windows, it just means you don't need to (especially in winter).

 

Your slab design does not sound insulated from the ground so cold bridging needs to be considered (as it does in the frame) and you should have an idea of the flow temp your UFH will need. Genuine low energy builds require low flow temps and usually no space heating upstairs as the heat requirement is quite low. ASHP can cool an insulated slab effectively. If you have plenty of PV then this is an efficient way to keep the house cool in summer.

 

If your architect is genuinely experienced at 'eco' builds they should know all of this, they should also have a target SAP or better to understand how the house will perform and its space heat requirement etc. Have you seen that?

 

 

[SteamyTea]

Have you got your self build Community Infrastructure Levy exception in place (if your local authority has one).

 

Cooling a building is the same as heating one. Work out the heat gains and the temperature differences, and that is the size of system needed. The rest is detail, i.e. condensation risk, slab or forced air.

[ukjamie]

4 hours ago, Nickfromwales said:

Hi and welcome to the forum. 
From what you’re saying here, and above, you may already have the horse and the cart the wrong way ‘round  

MVHR cannot be ‘on the table’ if the intention is to go for air tightness that is excellent. You’ll choke on your own fumes without MVHR, for one, plus to be “green” or “eco” ( terms often used very loosely, and more often with a complete lack of understanding of what that is supposed to deliver to you in this reasonably unique build ) you will 100% need to be actively recovering waste heat for re-introduction through the MVHR system! Building control will demand your as built air tightness ( ventilation / infiltration ) results to be sure you have adequate numbers of air changes per hour. If all the above is known, how do you propose to meet those requirements? Make the house AT and then fit loads of trickle vents? ?. 
All these questions need firm and robust answers BEFORE pressing ANY more buttons.

I’m currently providing M&E for such a dwelling ( pool etc ) and the design work was enormous. The pool hall will need its own envelope as the dehumidification and heat recovery system typically runs at a slight negative pressure to preserve the build fabric, therefore it should not be able to ‘share’ the air volume of the residential section of the dwelling. Forget recovering heat from the pool hall, as every ounce of that will be absolutely needed to maintain the temps in the pool hall!! How big is the pool? Is it a pre-fab that you are “dressing” into the house 
Lots and lots of things here will impact on the others, so measure twice cut once ?

Cheers Nick. I have been addressing the obvious floors in our plans today and spoken with the designers. They are on the case as of now. there is no real time scale for the build. The pool will be outdoors, so no issues with temps, apart from water that is.Thanks again.

[ukjamie]

1 hour ago, Bitpipe said:

 

Solar gain is usually a function of how much glass you have, the orientation and external shading. The frame fabric can help but usually requires a high decrement delay type insulation like blown cellulose.

 

Once a moderately well insulated building overheats due to to much solar gain through the windows, it is difficult to cool it down, so effective shading is really important - be that trees, bris soleil, external shutters or reflective film/glass. Overheating can happen year round, not just in summer and is actually more prevalent in spring and autumn when the sun is lower in the sky and can penetrate deeper into the house. A stack ventilation strategy (e.g. high level velux) can help flush the house with cool air at night and good airtightness will keep that cool air in the house for the following day. MVHR will keep air fresh and humidity low.

 

Also be aware that air tightness is the responsibility of all trades - great the the frame company seem to commit to it but this needs to extend to the window fitters and any trade that penetrates the envelope, like electricians or plumbers. All penetrations need to be taped and sealed, one careless trade can render the whole airtightness void. Your blower test will show the result but it can be hard to rectify issues if the house is largely complete and the problems are hidden.

 

As Nick says, MVHR is a must if your house is anyway airtight otherwise you will have no fresh air without trickle vents in windows and then all your precious heat is freely leaving the house which will drive up running costs. MVHR does not mean you can't open doors & windows, it just means you don't need to (especially in winter).

 

Your slab design does not sound insulated from the ground so cold bridging needs to be considered (as it does in the frame) and you should have an idea of the flow temp your UFH will need. Genuine low energy builds require low flow temps and usually no space heating upstairs as the heat requirement is quite low. ASHP can cool an insulated slab effectively. If you have plenty of PV then this is an efficient way to keep the house cool in summer.

 

If your architect is genuinely experienced at 'eco' builds they should know all of this, they should also have a target SAP or better to understand how the house will perform and its space heat requirement etc. Have you seen that?

 

 

Quite the eye opener all of this sound advice. One thing we are doing is insulating the slab. But the MVHR needs to be discussed with my architect as I have not reall had any info for any of this. Thanks bud

[SteamyTea]

8 minutes ago, ukjamie said:

One thing we are doing is insulating the slab

To building regs minimum or better?

[IanR]

18 minutes ago, ukjamie said:

The pool will be outdoors.

 

Have you had an outdoor pool before?

 

Never, ever again for me. Although, mine was a '90's built Penguin pool, with an uninsulated concrete tub. So, on top of the time it took keeping it looking OK, the cost to heat was ridiculous.

Edited September 3, 2021 by IanR

[scottishjohn]

4 hours ago, pdf27 said:

They arguably make economic sense if you need a ton of heating, where the improved efficiency in winter starts to save a reasonable amount of cash. Otherwise, it's very difficult to figure out ways where a GSHP is cheaper than an ASHP over the lifetime of the equipment. It's worth noting that for year-round heat loads (hot water and potentially a swimming pool), a GSHP doesn't add value: ground temperature is the same as the average air temperature where you are, lower if you start pulling heat out of it. That means if you use a lot of heat in summer 

 

We're looking at GSHP, but it's fairly special circumstances - heating load is small (2kW) so the cost differential isn't too big, our garden is big enough for the ground loop to go in trenches and I hate the aesthetics of an ASHP outdoor unit. Provided the cost differential can be kept down to a couple of thousand, GSHP is the better option for us. Playing around with spreadsheets suggests that the electricity consumption difference over the course of a year is probably within 100kWh or so however!

gshp have a  definite  advantage when you have a climate where winter temps are -10 c or -20c more for months like Canada or very northern Europe--that when  the better COP at lower ambient  temps will pay back --but thats not the uk.

 don,t forget much higher servicing costs and changing the fluid inthe underground coils every now and then 

if its just the look of the ASHP unit ,then move it further away from house or plant things around?

Edited September 3, 2021 by scottishjohn

[Nickfromwales]

44 minutes ago, IanR said:

 

Have you had an outdoor pool before?

 

Never, ever again for me. Although, mine was a '90's built Penguin pool, with an uninsulated concrete tub. So, on top of the time it took keeping it looking OK, the cost to heat was ridiculous.

Unless even poorly covered ( with a building of sorts ) then the expense will be eye-watering to keep this warm, forget hot. Ouch. 
My advice would be about 15kW of solar thermal dedicated to just this, with excess diverted into the domestic hot water ( DHW ) cylinder, so at least it’ll have the chill off it for most of the year. Heating during the colder parts of the year would need a direct ‘pool’ ASHP. 

Did I say ouch?

Edited September 3, 2021 by Nickfromwales

[Adrian Walker]

7 hours ago, ProDave said:

ECO build and "pool" (with all the energy that uses) seems slightly contradictory?

 

 

 

A pool is a perfect way to store and extract heat.

[Adrian Walker]

2 minutes ago, Nickfromwales said:

Unless even poorly covered ( with a building of sorts ) then the expense will be eye-watering to keep this warm, forget hot. Ouch. 
My advice would be about 15kW of solar thermal dedicated to just this, with excess diverted onto the domestic hot water ( DHW ) cylinder, so at least it’ll have the chill off it for most of the year. Heating during the colder parts of the year would need a direct ‘pool’ ASHP. 

Did I say ouch?

 

 

If it's full insulated a pool will be fine.  If you have water source heat pump you should get CoP of 6

[IanR]

1 minute ago, Adrian Walker said:

  If you have water source heat pump you should get CoP of 6

 

I'm not sure I've understood, wouldn't you need a handy hot spring in the garden to heat a pool with a COP of 6 using a water source heat pump.

 

Where are you moving energy from and to with this WSHP?

[Ferdinand]

2 hours ago, ToughButterCup said:

 

Welcome.

'Waste time' on BuildHub. Often repays the effort. If nowt else is 'on' there's Good Sport to be had watching some of the regulars needling  Mods. Saints, all of them. ?

 

Saints as in Saint Sebastian.

 

(Tied to a tree and shot with arrows)

[Ferdinand]

On the house, I would pause once the weather goes, and do some careful thinking / analysis in the time before Christmas and restart next spring. I think there is a lot of detail that is best sweated now, rather than when you have to change it later.

 

Read some of the site blogs.

For the pool, have you considered a natural swimming pool?

 

You don't need heating; you just need not to be a wuss.

 

 

Though that diving ledge looks dodgy at first glance:

 

 

 

 

[Nickfromwales]

18 minutes ago, Adrian Walker said:

 

 

If it's full insulated a pool will be fine.  If you have water source heat pump you should get CoP of 6

Could you elaborate re the water source?

[Adrian Walker]

6 minutes ago, Nickfromwales said:

Could you elaborate re the water source?

 

 

I think he said that he had a bore hole for water and also the pool might be inside

[Nickfromwales]

8 minutes ago, Adrian Walker said:

I think he said that he had a bore hole for water and also the pool might be inside

  

Let’s see what the OP says will be the plan for the pool and then we can properly rip into him lol. ?

[ToughButterCup]

A cold-water pool is  the  key to health and happiness. Yep, its a shock to the system, but it's addictive. Cheaper too.

[pdf27]

1 hour ago, scottishjohn said:

don't forget much higher servicing costs and changing the fluid in the underground coils every now and then 

if its just the look of the ASHP unit ,then move it further away from house or plant things around?

Should be very little to actually service for any sort of heat pump however, and I'd note that while the glycol will eventually need changing deterioration tends to happen at high temperatures rather than low ones so life should be pretty long in a GSHP application.

ASHP is feasible if the costs come back too high, the current expectation is that the cost of a 3kW GSHP (options are Kensa Shoebox or Nilan compact unit) and installation will be no more than £2-3k above the cost of an ASHP which is borderline acceptable.

[ukjamie]

2 hours ago, SteamyTea said:

To building regs minimum or better?

Better. 

[ukjamie]

1 hour ago, Ferdinand said:

On the house, I would pause once the weather goes, and do some careful thinking / analysis in the time before Christmas and restart next spring. I think there is a lot of detail that is best sweated now, rather than when you have to change it later.

 

Read some of the site blogs.

For the pool, have you considered a natural swimming pool?

 

You don't need heating; you just need not to be a wuss.

 

 

Ha ha ha. I have three kids who are wusses!

[ukjamie]

1 hour ago, Nickfromwales said:

  

Let’s see what the OP says will be the plan for the pool and then we can properly rip into him lol. ?

 

1 hour ago, Nickfromwales said:

  

Let’s see what the OP says will be the plan for the pool and then we can properly rip into him lol. ?

Had this in mind...

[Ferdinand]

This?

 

[Ferdinand]

Or this?

 

[Patrick]

9 hours ago, ukjamie said:

Eco build with a pool does seem contradictory, yes! Loads of solar, ground source heating, bore hole water...should save quite a bit on energy bills. No straw walls, just a timber framed build and dare I say, we are having air con too!

So its a "eco-just-in-the-name-build" ? . Welcome to the forum. It is the most helpfull source of information out there. The great thing about it is, that each can find their own type of "mentor" to listen too , some like it more technical - others, like me, are illiterate idiots and need everything explained with pictures or videos...

Both can be found here.

[ProDave]

If I wanted an unheated outdoor pool, it's either the river, a 5 minute walk from home, or the sea, 3 miles from home.  Neither are what you would call "warm"

 

The council run public pool 7 miles away is infinitely more inviting.