Wow !..........so much to learn and so little time !

[Russell griffiths]

11 minutes ago, NSS said:

Don't do it! If there's one sure way to ensure it ends up looking like a dog's breakfast, it's to design by committee ?

This is very true, one reason I have never posted my floor plans is I dont really want other people’s opinions, I’m building it for me and the wife and we live very different lives to most people. 

Decide what you want and then ask for good ways to achieve this, not what would you build. 

[Canoehq]

Just now, Thedreamer said:

@Canoehqare you up to speed on VAT rules for barn conversions?

 

 

Well I know it's not zero rated because not a new build, so had assumed it was the next band up at 5%.  Is that right ?

[Nickfromwales]

Good news then, you can get a decent, well insulated slab down and use that to smooth the heating peak demand. ASHP will lend itself perfectly, and slab / duct cooling will be a very good friend of yours. 

2x the bang for 1x ASHP bucks. ?.

Do you have permission for solar PV? Stay away from solar thermal as you’ll have an “all electric house” and nowhere to utilise the excessive amounts of heat ST would give through the summer.

The PV would, however, run all the cooling FOC when the thing shining on the roof causing the problems also lends itself to off-setting the costs of mitigating against it.

Focus on air tightness, and max out on insulation to suit the budget. For eg, you should be going for a minimum of 200mm of insulation under a HEATED slab.  

If you can’t get to that standard all is not lost, as at the end of the day the ASHP is a multiplier so for every 1kW used, you’ll get around 2.5-3kW heat out of it. 

Get an early design SAP / DER and also see if you’d benefit from RHI at all. If it breaks you even on the cost of the install that would be something towards the kitchen  . If the EPC is v. good - excellent then RHI probably won’t be significant enough to cover the elevated ( MCS accredited ) installation. Most of my clients have been persuaded away when seeing “the numbers”.    

[Thedreamer]

11 minutes ago, Canoehq said:

Well I know it's not zero rated because not a new build, so had assumed it was the next band up at 5%.  Is that right ?

 

5%, I take it your going down the main/building contractor route supplying labour and materials.

 

I would do plenty of research here so you are fully aware of the VAT position (and then make sure your contractor is as well!), so you don't have any unexpected surprises. 

 

 

 

Edited September 22, 2019 by Thedreamer

[Canoehq]

4 minutes ago, Nickfromwales said:

Good news then, you can get a decent, well insulated slab down and use that to smooth the heating peak demand. ASHP will lend itself perfectly, and slab / duct cooling will be a very good friend of yours. 

2x the bang for 1x ASHP bucks. ?.

Do you have permission for solar PV? Stay away from solar thermal as you’ll have an “all electric house” and nowhere to utilise the excessive amounts of heat ST would give through the summer.

The PV would, however, run all the cooling FOC when the thing shining on the roof causing the problems also lends itself to off-setting the costs of mitigating against it.

Focus on air tightness, and max out on insulation to suit the budget. For eg, you should be going for a minimum of 200mm of insulation under a HEATED slab.  

If you can’t get to that standard all is not lost, as at the end of the day the ASHP is a multiplier so for every 1kW used, you’ll get around 2.5-3kW heat out of it. 

Get an early design SAP / DER and also see if you’d benefit from RHI at all. If it breaks you even on the cost of the install that would be something towards the kitchen  . If the EPC is v. good - excellent then RHI probably won’t be significant enough to cover the elevated ( MCS accredited ) installation. Most of my clients have been persuaded away when seeing “the numbers”.    

Seriously good advice, thank you.  Re Solar PV, didn't honestly think the pay back numbers worked for us as we head to retirement in a few years, but will re-visit.

Also, never seen such a hike in fees using an MCS installer compared to what a switched on heat engineer and a six month old ASHP would cost me !

 

7 minutes ago, Thedreamer said:

 

5%, I take it your going down the main/building contractor route supplying labour and materials.

 

I would do plenty of research here so you are sure you fully aware of the VAT position (and then make sure your contractor is as well!), so you don't have any unexpected surprises. 

 

 

 

  Yes, have appointed a project manager who will arrange all of the works and building supplied as needed.  Even though he's not VAT registered, if I order directly, that's 5% right ?

[Jeremy Harris]

7 minutes ago, Canoehq said:

  Yes, have appointed a project manager who will arrange all of the works and building supplied as needed.  Even though he's not VAT registered, if I order directly, that's 5% right ?

 

 

If you order directly, then you will pay VAT at 20% on materials, but be able to claim back 15% of that from HMRC on completion.  There's a useful VAT thread here that goes through all the intricacies of VAT reclaim that is worth a read, as there are some potential gotchas to look out for.

 

 

PV is probably of far more benefit for a house like yours, where you are likely to have a high risk of overheating and a need for active cooling for a fair part of the year.  The PV offsets the cost of cooling (which may well be much greater than the cost of winter heating), so the sums look more favourable.  If roof mounted, the PV panels also reduce solar gain into the roof by about 20%, as they turn that energy into electricity, so it's a bit of a win-win really.

 

 

[Thedreamer]

https://forum.buildhub.org.uk/topic/6851-a-guide-to-the-vat-reclaim-process/

 

@Canoehq the thread that @JSHarris mentioned.

[Canoehq]

1 minute ago, JSHarris said:

 

 

If you order directly, then you will pay VAT at 20% on materials, but be able to claim back 15% of that from HMRC on completion.  There's a useful VAT thread here that goes through all the intricacies of VAT reclaim that is worth a read, as there are some potential gotchas to look out for.

 

 

PV is probably of far more benefit for a house like yours, where you are likely to have a high risk of overheating and a need for active cooling for a fair part of the year.  The PV offsets the cost of cooling (which may well be much greater than the cost of winter heating), so the sums look more favourable.  If roof mounted, the PV panels also reduce solar gain into the roof by about 20%, as they turn that energy into electricity, so it's a bit of a win-win really.

 

 

Hadn't quite thought of it like that and contemplating the high levels of cooling I may actually need if I can't get these windows / glass right.  Have had a look at the cost of the Sage glass you suggested and had to sit down !  There must be a cheaper (albeit not simpler) way of dealing with this gain or stopping it entering in the first place.

 

PV may be a good plan indeed, but it can't be roof mounted, as feel sure the planners would not allow.........and it's a round rook also, so may look a bit odd !

Have enough land at the bottom of the garden to install there though and in the middle of what was going to be a conservation wild meadow, bees etc.

[Canoehq]

Just now, Thedreamer said:

https://forum.buildhub.org.uk/topic/6851-a-guide-to-the-vat-reclaim-process/

 

@Canoehq the thread that @JSHarris mentioned.

Thank you again Mr Dreamer !

[ragg987]

26 minutes ago, Canoehq said:

There must be a cheaper (albeit not simpler) way of dealing with this gain or stopping it entering in the first place.

Tall trees south of your house? If not then you have shutters or brise-soleil in addition to reflective glass or films. You might get a combination e.g. short-overhang brise and shorter trees.

[Canoehq]

@JSHarris  I'm intrigued at your last comment and perhaps beginning to fully understand what you meant.  May I ask you a quick question ?

 

So in trying to keep things extremely simple so that I can understand them, are you suggesting this comes down to a simple choice between;

 

1. Hugely expensive Sage glass windows (to keep the solar gain to a minimum);  versus

2. Admitting defeat on much of the solar gain and using cheaper standard solar reducing glass but with a PV system running alongside to provide active cooling almost 24/7 if needed ?

 

Is that the nub of it ?

 

My early thoughts are to go with the second option, but we have a very eco-concious planning dept and would hate to upset them with a PV / aircon system running almost day and night !

 

 

Edited September 22, 2019 by Canoehq

[ragg987]

Or maybe a mesh screen? Might create an interesting effect.

 

We were soaking up winter sun in India at christmas - their architects really understood the effect of screening to aid cooling - shading and ventilation - plus privacy.

[Canoehq]

16 minutes ago, ragg987 said:

Tall trees south of your house? If not then you have shutters or brise-soleil in addition to reflective glass or films. You might get a combination e.g. short-overhang brise and shorter trees.

No, just a beautiful open view to the River Stour, so can't complain !

 

 

Won't be allowed brise soleil unfortunately, as anything that sticks out over the footprint of the barn is a no-no with the Planners I'm afraid.

So, shutters it may have to be.

 

Brilliant idea about the screening, but would hate the interior to become too dark.

 

Edited September 22, 2019 by Canoehq

[ragg987]

5 minutes ago, Canoehq said:

but would hate the interior to become too dark

It is a balance - anything you do to reduce direct light coming into the house (film, trees etc) will mean you are making it darker.

 

6 minutes ago, Canoehq said:

brise soleil unfortunately, as anything that sticks out over the footprint

Brise does not have to stick out by much - you can have window slats, random google search: http://dougintology.blogspot.com/2007/11/solar-decathlon-window-slats.html

 

8 minutes ago, Canoehq said:

No, just a beautiful open view to the River Stour, so can't complain !

Sounds really nice...

[Canoehq]

2 minutes ago, ragg987 said:

It is a balance - anything you do to reduce direct light coming into the house (film, trees etc) will mean you are making it darker.

 

Brise does not have to stick out by much - you can have window slats, random google search: http://dougintology.blogspot.com/2007/11/solar-decathlon-window-slats.html

 

Sounds really nice...

What a fantastic forum !

[Onoff]

1 hour ago, Nickfromwales said:

Stay away from solar thermal

 

How about a nice line of evacuated tubes rolled to follow the roof profile then a small steam turbine?

 

I'll get me coat...

[ProDave]

1 hour ago, Canoehq said:

Seriously good advice, thank you.  Re Solar PV, didn't honestly think the pay back numbers worked for us as we head to retirement in a few years, but will re-visit.

Also, never seen such a hike in fees using an MCS installer compared to what a switched on heat engineer and a six month old ASHP would cost me !

 

There is no longer any Feed In Tariff for solar PV.  That also means there is no longer any need to use an MCS installer.  Yoi can DIY install it, or just pay any competent electrician to install it.

 

I did my own at the beginning of this year. By DIY and shopping around a LOT I got it down to £1500 and I am on target to self use £250 worth of electricity giving a payback time of 6 years.

 

Given your roof, and the fact you have plenty of land, I would go for a ground mount system, which also makes it a lot easier to DIY as no high up on roof work.

 

As already mentioned, the solar PV would power the ASHP for most of the summer while it is cooling the house so you get the cooling for free and it should be pretty easy to self use all that you generate.

 

Also re the ASHP and MCS.  A lot of us have found that is is simply not worth paying the inflated MCS prices just so you can claim the RHI payment, which might be small for a well insulated house.  Just buy the ASHP as cheap as you can and install yourself or any competent plumber and electrician can install it and forget the RHI.  No need to buy second hand, some new bargains come up from time to time.

[Canoehq]

4 minutes ago, ProDave said:

There is no longer any Feed In Tariff for solar PV.  That also means there is no longer any need to use an MCS installer.  Yoi can DIY install it, or just pay any competent electrician to install it.

 

I did my own at the beginning of this year. By DIY and shopping around a LOT I got it down to £1500 and I am on target to self use £250 worth of electricity giving a payback time of 6 years.

 

Given your roof, and the fact you have plenty of land, I would go for a ground mount system, which also makes it a lot easier to DIY as no high up on roof work.

 

As already mentioned, the solar PV would power the ASHP for most of the summer while it is cooling the house so you get the cooling for free and it should be pretty easy to self use all that you generate.

 

Yes and I have an electric car also !

 

But for 4kw +, it would be way bigger than the 9 sq m allowed for the permitted development install, so back to the planners ..........groan !

Edited September 22, 2019 by Canoehq

[Jeremy Harris]

1 hour ago, Canoehq said:

@JSHarris  I'm intrigued at your last comment and perhaps beginning to fully understand what you meant.  May I ask you a quick question ?

 

So in trying to keep things extremely simple so that I can understand them, are you suggesting this comes down to a simple choice between;

 

1. Hugely expensive Sage glass windows (to keep the solar gain to a minimum);  versus

2. Admitting defeat on much of the solar gain and using cheaper standard solar reducing glass but with a PV system running alongside to provide active cooling almost 24/7 if needed ?

 

Is that the nub of it ?

 

My early thoughts are to go with the second option, but we have a very eco-concious planning dept and would hate to upset them with a PV / aircon system running almost day and night !

 

 

 

 

Sage glass isn't that expensive when compared to things like solar control films - for us using Sage glass would have been maybe 20% more expensive that what we ended up doing, which was having solar control film applied to 3G glazing.  There are alternative ways to reduce solar gain using glass, by opting for glass that is designed to reflect heat outwards.  It's the stuff that's typically used in offices that have a large glazing area, where solar gain can be a real problem.

 

The advantage of Sage glass (and it is a very big advantage) is that it's controllable.  In summer you can turn the solar gain right down, in winter you can turn it up.  At least one member here has it, @NSS, and finds it works extremely well.

 

My inclination would be to massively reduce the glass area, but place the glazing so that it frames the views you have.  Often framing a view can make it more attractive than just having a vast expanse of glass, especially if you have those framed views arranged so that they provide a different aspect of the view.  Rather than limit the impact of the view, often framing it can enhance it and make it more interesting, as the light changes from one window to another.  It needs some expertise to get right, but when it is done well the result can be stunning, and add to the "wow factor" rather than subtract from it.  The key is to get an architect that understands this, as in many ways just fitting floor to ceiling glass is a cop out, as it doesn't require as much careful thought and ability to produce the view you want to be able to see.

 

As a rough rule of thumb, the very best glazing available will be around 4 times worse than an average wall, in terms of thermal efficiency.  Average glazing may well be 8 times worse than a wall.  Thermal efficiency works both ways, not only does it keep the house warmer in winter, but it also keeps it cooler in summer.

 

In terms of using PV to run an ASHP in cooling mode, then this can work very well, but it's still worth considering how much heat might need to be pumped out of the house.  Good glazing, with a fairly high external reflectance, might allow in about 100 to 200W per m² of glazing area.  Fairly standard glazing will be around 3 to 4 times that figure.  You can work out how much heat that is in total by just multiplying the area of glass that will be exposed to the sun, as that will give you the rough cooling requirement.  Using your figure of 150m² of glass, then with an optimistic solar gain of around 100 W/m² that's a 15 kW cooling requirement, which is pretty high.  Worst case for normal glazing might be a cooling requirement of over 100 kW.

 

To put this into perspective, our house is smaller than yours, at 130m² (about 1,400ft²) and has ~ 11m² of South facing glazing, that is covered with solar reflective film (we added the film as the house overheated very badly).  We have 25 solar panels in the South-facing roof that reduces the solar gain a bit and generates a maximum of around 6.25 kW of power.  For around 8 months of the year we have to use  active cooling,  using floor cooling from our 6 kW ASHP, cooling from our 1.5 kW active MVHR system and cooling in our bedroom using a 2.5 kW air conditioning unit that I installed this summer for additional cooling. 

 

Without active cooling our house that is around half the size of yours, with less than 1/10th of the South facing glazing area, would seriously overheat from around April until October.  We are in a sheltered valley, though, with low wind speeds, and a mean air temperature that's a degree or two warmer than typical for this area.

[newhome]

Welcome!

 

To clarify the VAT postion, your conversion is either eligible for the VAT reclaim scheme or it's not. On the surface it looks as if it could well be. Read the notes in this link carefully to ensure that you qualify as the reclaim is at the end of the project so there is a lot of money at stake.  

 

VAT431C

 

If you do qualify it works like this (all of this is in the link posted above but to summarise here):

• Any materials you buy yourself (must be in your name) you pay 20% VAT and can reclaim ALL of the 20% back via the reclaim scheme
• Any labour from a VAT registered trader is @ 5% and then you reclaim that 5% via the reclaim scheme
• Any supply and fit arrangements by a VAT registered trader are @ 5% (the whole invoice) and then you reclaim that 5% via the reclaim scheme
• If you use a non VAT registered trader for work they will need to charge you full VAT on materials as they don't have any way of reclaiming it themselves via a VAT return so if you are using non VAT registered traders try to supply the materials yourself (invoices in YOUR name) so that you can reclaim the VAT

Ultimately you should get all of the VAT back (on eligible items and work) if your conversion is eligible and it will put you in the same position as a new build. There are lots of other details in that thread about what is eligible and when things can be 'zero rated'. For new builds labour and supply & fit are zero rated so where you read 'zero rated' for a conversion replace that with '5% rated of which that 5% can be reclaimed at the end of the build'. Pretty much everything else is the same. 

 

If you have any specific questions about VAT pop a reply on the other thread so that it keeps it all in one place. 

[Canoehq]

15 minutes ago, JSHarris said:

 

 

Sage glass isn't that expensive when compared to things like solar control films - for us using Sage glass would have been maybe 20% more expensive that what we ended up doing, which was having solar control film applied to 3G glazing.  There are alternative ways to reduce solar gain using glass, by opting for glass that is designed to reflect heat outwards.  It's the stuff that's typically used in offices that have a large glazing area, where solar gain can be a real problem.

 

The advantage of Sage glass (and it is a very big advantage) is that it's controllable.  In summer you can turn the solar gain right down, in winter you can turn it up.  At least one member here has it, @NSS, and finds it works extremely well.

 

My inclination would be to massively reduce the glass area, but place the glazing so that it frames the views you have.  Often framing a view can make it more attractive than just having a vast expanse of glass, especially if you have those framed views arranged so that they provide a different aspect of the view.  Rather than limit the impact of the view, often framing it can enhance it and make it more interesting, as the light changes from one window to another.  It needs some expertise to get right, but when it is done well the result can be stunning, and add to the "wow factor" rather than subtract from it.  The key is to get an architect that understands this, as in many ways just fitting floor to ceiling glass is a cop out, as it doesn't require as much careful thought and ability to produce the view you want to be able to see.

 

As a rough rule of thumb, the very best glazing available will be around 4 times worse than an average wall, in terms of thermal efficiency.  Average glazing may well be 8 times worse than a wall.  Thermal efficiency works both ways, not only does it keep the house warmer in winter, but it also keeps it cooler in summer.

 

In terms of using PV to run an ASHP in cooling mode, then this can work very well, but it's still worth considering how much heat might need to be pumped out of the house.  Good glazing, with a fairly high external reflectance, might allow in about 100 to 200W per m² of glazing area.  Fairly standard glazing will be around 3 to 4 times that figure.  You can work out how much heat that is in total by just multiplying the area of glass that will be exposed to the sun, as that will give you the rough cooling requirement.  Using your figure of 150m² of glass, then with an optimistic solar gain of around 100 W/m² that's a 15 kW cooling requirement, which is pretty high.  Worst case for normal glazing might be a cooling requirement of over 100 kW.

 

To put this into perspective, our house is smaller than yours, at 130m² (about 1,400ft²) and has ~ 11m² of South facing glazing, that is covered with solar reflective film (we added the film as the house overheated very badly).  We have 25 solar panels in the South-facing roof that reduces the solar gain a bit and generates a maximum of around 6.25 kW of power.  For around 8 months of the year we have to use  active cooling,  using floor cooling from our 6 kW ASHP, cooling from our 1.5 kW active MVHR system and cooling in our bedroom using a 2.5 kW air conditioning unit that I installed this summer for additional cooling. 

 

Without active cooling our house that is around half the size of yours, with less than 1/10th of the South facing glazing area, would seriously overheat from around April until October.  We are in a sheltered valley, though, with low wind speeds, and a mean air temperature that's a degree or two warmer than typical for this area.

Just a huge thank you for taking the trouble to reply in such detail.  Lots to think about.

 

The last figures I spotted on here for sage glass were about £1k per m2 which would be way out of the ball park for me.  But if I could find a reasonably priced supplier, then perhaps it could be back on the table.

 

Again, thank you.

[Canoehq]

4 minutes ago, newhome said:

Welcome!

 

To clarify the VAT postion, your conversion is either eligible for the VAT reclaim scheme or it's not. On the surface it looks as if it could well be. Read the notes in this link carefully to ensure that you qualify as the reclaim is at the end of the project so there is a lot of money at stake.  

 

VAT431C

 

If you do qualify it works like this (all of this is in the link posted above but to summarise here):

• Any materials you buy yourself (must be in your name) you pay 20% VAT and can reclaim ALL of the 20% back via the reclaim scheme
• Any labour from a VAT registered trader is @ 5% and then you reclaim that 5% via the reclaim scheme
• Any supply and fit arrangements by a VAT registered trader are @ 5% (the whole invoice) and then you reclaim that 5% via the reclaim scheme
• If you use a non VAT registered trader for work they will need to charge you full VAT on materials as they don't have any way of reclaiming it themselves via a VAT return so if you are using non VAT registered traders try to supply the materials yourself (invoices in YOUR name) so that you can reclaim the VAT

Ultimately you should get all of the VAT back (on eligible items and work) if your conversion is eligible and it will put you in the same position as a new build. There are lots of other details in that thread about what is eligible and when things can be 'zero rated'. For new builds labour and supply & fit are zero rated so where you read 'zero rated' for a conversion replace that with '5% rated of which that 5% can be reclaimed at the end of the build'. Pretty much everything else is the same. 

 

If you have any specific questions about VAT pop a reply on the other thread so that it keeps it all in one place. 

And thank you.  So much reading ahead and just as I thought I was starting to swim, I've just gone under water for the first time !

 

Thanks to everyone so far. 

[Jeremy Harris]

16 minutes ago, Canoehq said:

Just a huge thank you for taking the trouble to reply in such detail.  Lots to think about.

 

The last figures I spotted on here for sage glass were about £1k per m2 which would be way out of the ball park for me.  But if I could find a reasonably priced supplier, then perhaps it could be back on the table.

 

Again, thank you.

 

 

Worth looking at glazing cost comparatively.  With that area of glazing you are going to have to use some fairly high specification 3G glazing, most probably with laminated glass for a lot of it.  Sage glass is going to roughly double the cost at a guess, and will allow solar gain to be reduced to maybe 50 W/m² in hot, sunny, weather, a big improvement, but it will still mean having maybe 7.5 kW of active cooling for worst case days.

 

Using solar reflective glass will give about the same results as using Sage glass, for maybe half the cost, so will still need a fair bit of active cooling.  The main disadvantage of using solar reflective glass is that you will also need more heating in winter, as there will be much less solar gain during the four months or so of the year when it might be useful.  The cost of that additional heating may well equal the additional cost of Sage glass over solar reflective glass after a few years.

 

Realistically, I think you'll be looking at a glazing cost, including frames, just using conventional glass, with the required laminated panes,  of around £450 to £500/m² at the budget end.  You can get really budget windows for around £300/m², but not with the large areas of laminated glass you are almost certainly going to need, and not with the thermal performance that you will need to try and meet the regs requirements.  I think you may really struggle with meeting the regs with 150m² of the very best glazing available, TBH, hence the earlier comment that doing a SAP assessment of the design now may well make a lot of sense, before you get too committed.  If that shows that there is just too much heat loss through the glazing then you are going to need to have a re-think anyway, and better to do that before you've gone too far down the road at looking at different glazing options, perhaps.

[SteamyTea]

1 hour ago, Onoff said:

How about a nice line of evacuated tubes rolled to follow the roof profile then a small steam turbine?

 

I'll get me coat...

Not such a stupid idea, in a way.

You could you that large tin roof to heat an evaporative cooler.

https://en.wikipedia.org/wiki/Evaporative_cooler

[Bitpipe]

1 hour ago, Canoehq said:

 

So, shutters it may have to be.

 

Brilliant idea about the screening, but would hate the interior to become too dark.

 

 

We have external motorised blinds (Roma, venetian style) to windows at the front of our house which faces east so gets lots of morning sun.

 

While the blinds fully recess above the windows we only really do that for occasional cleaning (and as the windows open inwards, even that is not necessary).

 

Instead they are about 50% inclined when sun is up, flat for the rest of the day and closed at night for privacy - there really is not a noticeable impact on light when they're flat.

 

Even when its very windy there is little rattle as there is a U channel on the side of each window and every other blind locks into this - wind robustness is definitely something to consider as some designs need to be retracted in heavy wind or they risk damage.

 

I also believe there is a maximum width with that type of blind 4m or something, so you may want to take that into consideration when designing the windows.

 

Internorm do an internal blind, it sits behind the first pane and in front of a double glazed unit but I really did not like it, looked flimsy.