Concerned about solar heat gain

[Bancroft]

23 hours ago, flanagaj said:

do these 'fan coils' require some sort of condensation drain.

I'm still investigating this and haven't yet fitted so take read this with caution.

 

Condensation drains? I think the basic answer is 'yes'.

 

However, if thought about early enough in the planning process it shouldn't be too much of an issue.  I'm planning on 4-5 fan coil heads in a single storey building and (on paper) it doesn't seem too torturous to find ways to locate the fan coil where drains will be easy to install.  For example, we have two bedrooms with a bathroom in the middle - easy to mount the units on the bathroom/bedroom wall and take the drain through the wall into the bathroom plumbing.  Ditto near the kitchen etc.

 

Also, I think some units that can be ceiling mounted can pump condensate uphill to then flow down into the final drain.  This means easier installation between floors or routing through loft spaces.

[JohnMo]

18 minutes ago, Bancroft said:

I'm still investigating this and haven't yet fitted so take read this with caution.

 

Condensation drains? I think the basic answer is 'yes'.

 

However, if thought about early enough in the planning process it shouldn't be too much of an issue.  I'm planning on 4-5 fan coil heads in a single storey building and (on paper) it doesn't seem too torturous to find ways to locate the fan coil where drains will be easy to install.  For example, we have two bedrooms with a bathroom in the middle - easy to mount the units on the bathroom/bedroom wall and take the drain through the wall into the bathroom plumbing.  Ditto near the kitchen etc.

 

Also, I think some units that can be ceiling mounted can pump condensate uphill to then flow down into the final drain.  This means easier installation between floors or routing through loft spaces.

As soon as you flow water below dew point (let's say 12 degs) for more than a few minutes you will start to generate condensation. Target flow temps below dew point, you get condensation forming. Our summer house has a fan coil and have never seen a single drip from it. It flows from the same circuit as the house UFH.

[Nick Laslett]

On 02/07/2025 at 11:55, flanagaj said:

…do these 'fan coils' require some sort of condensation drain?

MVHR, A/C and ComfoPost all need condensate drains,
 

The planning and installation of all this stuff is where the professionals can really add their value.

 

Many different ways to route all this stuff, but really helps if you design it in from the beginning. Same with the external blinds. Just look at villas in Provence or Tuscany, they all have thick stone walls, small south facing windows with external timber shutters. 
 

If you can design in motorised external shutters, this would solve this problem. Won’t suit all house styles. 
 

Good video on this topic. 
 

 

Edited Thursday at 11:27 by Nick Laslett

[Bramco]

19 hours ago, flanagaj said:

All of these suggestions are great, but they all seem to come at a ridiculous cost and given we are already struggling to balance the numbers it just keeps spiralling.  We have been told that Solar glass is an 8% uplift so that is probably the cheaper option than fittings the blinds or AC/PV

Talk to Hallmark Blinds - I can't remember what ours cost but it wasn't prohibitive.  And you don't need anything fancy for the 'cassette' that the blinds park into when up. All you need is a properly sized gap behind the cladding, so that the blinds can be fitted into the gap.

[Thorfun]

20 hours ago, flanagaj said:

All of these suggestions are great, but they all seem to come at a ridiculous cost and given we are already struggling to balance the numbers it just keeps spiralling.  We have been told that Solar glass is an 8% uplift so that is probably the cheaper option than fittings the blinds or AC/PV

external blinds will mean you won't need internal curtains so the total cost is reduced when you consider that

 

speak to an AC company about costs for getting them to do first fix and then you can second fix at a later date when funds allow

 

there are ways to reduce the initial outlay of costs and some costs can be offset by mitigating the need for other things later. e.g. adding solar PV now will reduce the running costs of the house as you live in it. so you're, in essence, buying your electricity up-front until you get to the point that you've paid off the install and then you're getting free electricity!

[flanagaj]

6 hours ago, Bramco said:

Talk to Hallmark Blinds - I can't remember what ours cost but it wasn't prohibitive.  And you don't need anything fancy for the 'cassette' that the blinds park into when up. All you need is a properly sized gap behind the cladding, so that the blinds can be fitted into the gap.

Interesting product, but keen to understand the build up for a traditional masonry build with timber cladding.  The vertical timber cladding sits on two 25mm battens, so to have the blind hidden when open, will require an interesting and unconventional opening?

[flanagaj]

I came across these last night.  They look very good for bedrooms and are exactly what they fit on the continent.

External Roller Shutters | Enviroblinds

[Thorfun]

5 minutes ago, flanagaj said:

I came across these last night.  They look very good for bedrooms and are exactly what they fit on the continent.

External Roller Shutters | Enviroblinds

We went with Venetian so you can still see out while shading. 
 

https://www.hallmarkblinds.co.uk/external-blinds-and-shutters-uk

 

the Trojan ones. 

[flanagaj]

4 minutes ago, Thorfun said:

We went with Venetian so you can still see out while shading. 
 

https://www.hallmarkblinds.co.uk/external-blinds-and-shutters-uk

 

the Trojan ones. 

I will look at the Venetian offering.  Given it is just for the bedrooms, having them closed during the day is ok.  For us, it will come down to cost.

[Thorfun]

41 minutes ago, flanagaj said:

I will look at the Venetian offering.  Given it is just for the bedrooms, having them closed during the day is ok.  For us, it will come down to cost.

Sure. Cost is important. But so are aesthetics! I think there are so many factors to consider. 
 

it’s one of the reasons self-building is so stressful. All the decisions that need to be made from loads of various data points. 

[-rick-]

1 hour ago, flanagaj said:

I will look at the Venetian offering.  Given it is just for the bedrooms, having them closed during the day is ok.  For us, it will come down to cost.

 

I've seen a thread on here in the past about how the insect screens they had installed ended up being about perfect for shading too. Relatively cheap (as its simple roller blind) and maintains the view while cutting a lot of light. There are probably downsides too but worth considering as they will serve a dual purpose (though you will need curtains too if you want to black out the room).

[flanagaj]

One other question I have regarding the venetian or roller blinds is how they perform when it's windy.  Ideally, we would use them to black out the room and remove the need for curtains.   But this obviously only works if they don't rattle when it's blowing a gale straight at the window.

[Thorfun]

46 minutes ago, flanagaj said:

One other question I have regarding the venetian or roller blinds is how they perform when it's windy.  Ideally, we would use them to black out the room and remove the need for curtains.   But this obviously only works if they don't rattle when it's blowing a gale straight at the window.

One year in and no issues with this so far. 

[SBMS]

On 02/07/2025 at 14:24, Thorfun said:

we have an ASHP for hot water and ufh (downstairs). the AC can do heating for the bedrooms but we didn't need that last winter at all so it's primary job is cooling.

Did you do ducted AC upstairs or wall units?  Think we are going this direction..

[LnP]

On 03/07/2025 at 12:26, Nick Laslett said:

 

If you can design in motorised external shutters, this would solve this problem. Won’t suit all house styles. 
 

Good video on this topic. 
 

I'm a bit concerned that external  Venetian blinds will get dirty and dusty and be difficult to clean. Any issues with this?

I looked at these external screens at the NSBRC and they look quite interesting https://www.solar-shield.co.uk/microlouvre-screens. You can see through them but they claim to screen out enough to control solar gain. 

[Ferdinand]

A useful thread. I have 3 comments.

1 - For the benefit of future readers (apologies to OP formentioning) these are things that should really be considered before you get to planning permission stage. If it is something that has to be considered later then you end up spending more architect time, more planning consultant time and more planning fees for a second run round the block.

2 - For passive mitigations, I am a huge fan of pergolas of many sorts, including solar roofed. But consider access to upstairs walls and windows for cleaning / maintenance, whether you are going for a strong roof that can be walked on maybe with boards, a light roof so anybody will fall through it to make sure it *can't* be walked on. or indeed a balcony outside your bedrooms.

For the latter remember all those Deep Southern houses / cowboy towns in the American Dream, with all round parapets and balconies to keep the sun away.

And consider security wrt nimble scrotes or cat burglars (or cats) breaking in upstairs.

3 - As to active solutions, what about A2A heat pumps and solar? I will need to upgrade my gas fired underfloor central heating at some time in the next decade and A2A are the plan, despite having ufh downstairs and enlarged rads upstairs already in place. My ufh is not ideal (only 90mm of PIR insulation below the slab), and I have been running with a portable A2A heat pump unit on trial for a couple of years and my gas bills have plummeted.

[MikeSharp01]

On 02/07/2025 at 20:10, JohnMo said:

be pulling less than 500W (modulated down)

Does your ASHP modulate that far down, I have not found a 5kW one that will go below 1.8kW. 

[JohnMo]

17 minutes ago, MikeSharp01 said:

Does your ASHP modulate that far down, I have not found a 5kW one that will go below 1.8kW. 

I said pulling, as in pulling in electric. The graph of our ASHP was pulling in 840W it's a 6kW that modulates poorly. So see no reason why a 4kW ASHP  would need anything more than 500W, should be way less.

 

1.8kW is output heat I suspect.  So doing cooling could be pulling in 360W or less

[SteamyTea]

3 hours ago, Ferdinand said:

I have 3 comments.

Very valid points.

 

3 hours ago, Ferdinand said:

My ufh is not ideal (only 90mm of PIR insulation below the slab)

Especially this one, how often do we hear this.

3 hours ago, Ferdinand said:

I have been running with a portable A2A heat pump unit on trial for a couple of years

What model do you have, or can I borrow your unit when you have done with it.

[Thorfun]

10 hours ago, SBMS said:

Did you do ducted AC upstairs or wall units?  Think we are going this direction..

Ducted upstairs with the units in the loft and wall units downstairs. In hindsight I think ducted everywhere would’ve been better if possible and affordable. 

[Thorfun]

9 hours ago, LnP said:

I'm a bit concerned that external  Venetian blinds will get dirty and dusty and be difficult to clean. Any issues with this?

I looked at these external screens at the NSBRC and they look quite interesting https://www.solar-shield.co.uk/microlouvre-screens. You can see through them but they claim to screen out enough to control solar gain. 

We had a sample of this stuff and it was very impressive. But for some of the sizes of our windows we would’ve needed 2 panels per window and so would’ve had a line down the middle 

[JohnMo]

7 minutes ago, SteamyTea said:

portable A2A heat pump unit

There is a review of different makes and models in 'Which' some are really good others are pants. Best one cooled the test room from 35 to 25 in around 30 mins the worst was over 3 hrs.