Concerned about solar heat gain

[flanagaj]

Our approved plans are as below.  This is south facing and there is zero shading.  The architect hasn't specified eaves and I am concerned that unless we go with solar glass (already baulking at cost just for DG units), then the whole house will be unbearable during the warmer months.

Does anyone have any suggestions of things that we could potentially do.  We are submitting a NMA shortly and we could always put something on then.

[JohnMo]

External blinds are best, internal blinds ok. UFH run in cooling mode. Fan coils.

[joth]

Carefully planted and maintained trees can block summer sun but still let in some winter light. That tech is beyond me though (and takes time).

You could add brise soleil  to the plans, gives you the approval to install them if you ever want to in the future 

 

Else +1 for external shutter blinds, it's what the rest of Europe uses surely only time before we wake up to using them more here. 

[nod]

Thankfully we are north facing this time Our previous was south 

Our sun added a film to all the back windows that seem to work well 

[G and J]

1 hour ago, flanagaj said:

submitting a NMA shortly

Have you looked at part O yet? That may throw some changes into the mix

[flanagaj]

3 hours ago, JohnMo said:

External blinds are best, internal blinds ok. UFH run in cooling mode. Fan coils.

Keen to understand more about UFH running in cooling mode and using fan coils.  I understand the concept of switching the UFH into cooling mode, but interested to understand how you avoid condensation and do these 'fan coils' require some sort of condensation drain.

[flanagaj]

3 hours ago, joth said:

Carefully planted and maintained trees can block summer sun but still let in some winter light. That tech is beyond me though (and takes time).

You could add brise soleil  to the plans, gives you the approval to install them if you ever want to in the future 

 

Else +1 for external shutter blinds, it's what the rest of Europe uses surely only time before we wake up to using them more here. 

Given we are installing vertical timber cladding, these could in theory be added. without changing the appearance of the property.  Downstairs could be achieved using some sort of sun shade.

[SteamyTea]

21 minutes ago, flanagaj said:

but interested to understand how you avoid condensation and do these 'fan coils' require some sort of condensation drain.

Best to fit condensation drains of you can, it gives you the option to run them at a much lower temperature if you want to, though you have to be careful if running UFH(UFC really) at the same temperature, but if you have a reasonably sized concrete slab, it may take a few hours to drop the floor temperature to the dew point.

[JohnMo]

5 minutes ago, flanagaj said:

Keen to understand more about UFH running in cooling mode and using fan coils.  I understand the concept of switching the UFH into cooling mode, but interested to understand how you avoid condensation and do these 'fan coils' require some sort of condensation drain.

The way to operate is to run with a single flow temp for both fan coil and UFH. It means the fan coils are bigger for a given output in kW. But running everything above dew point, means no condensation, so no drains required.

 

A quick look at an online dew point calculation, house kept at 21, RH 60%, dew point is 12.9.

I set my target flow temperature at around that. I get no condensation on the UFH manifold. Floor surface temperature is around 19 to 20 depending on floor covering. So a mile away from condensation. The heat pump cycles based on return temp of around 19 degs. 

 

This is in the morning no solar gain

So short 10 min runs then off for an hour or so. 

 

This it when we get solar gain

Much longer runs.

 

When we get to heights of summer, the heat pump runs several hours at a time.

 

Our house internal temp almost all driven by solar gains, without internal blinds and UFH cooling our lounge l easily gets to 27 degs. Now it may go up to 24, but it recovers back sensibly levels quickly. But with a floor that is cooler than the air, it always feels cooler than it says on the a temperature gauge. Think old stone church always feels cool even when it's baking hot.

 

[flanagaj]

Does anyone have a link to fan coils as I have never heard of them before.

[Nick Laslett]

8 minutes ago, flanagaj said:

Does anyone have a link to fan coils as I have never heard of them before.

 
This is the Fancoil thread I have bookmarked. 
 

 

Panasonic have Fancoils and ASHPs. 

 

[Thorfun]

my 2 cents.....

 

1. external blinds are a must. plan them now so they can be built hidden in to the fabric of the house. we use ours to shade from the sun but also as curtains at night so don't have internal curtains for privacy.

 

2. just install AC

 

when i was researching i read a lot on here about fan coils and underfloor cooling etc and, in the end, it was just too complicated for me. not being able to heat water and cool the house at the same time just seemed a pain. so we planned for and installed ducted AC in the bedrooms and wall mounted units downstairs in a few rooms that we thought would need it. it is fabulous. the external blinds help and we have them automated to shade and follow the sun around but sometimes you just want to open them up fully and enjoy the view! so the AC takes care of the overheating and it's powered by the sun via our solar pv so i don't worry about running costs at all. our south facing bedroom has been a steady 21°C since April regardless of the outside weather.

 

keep it simple, install AC.

[Russdl]

5 hours ago, flanagaj said:

Does anyone have any suggestions of things that we could potentially do. 

You’ve got to start with external shading, prevention being better than cure and all that. East/west windows could be equally problematic. 
 

I’m sure you’ll be building with high levels of insulation and air tightness, in which case I would have thought that without shading/cooling the recent brief heatwave would have been unbearable. 

 

We have no cooling per se but we do have external blinds, the last few hot days have been a non event as far as internal temperature/comfort goes but that does require a very much non automated heat purging strategy of an evening (opening doors/windows, ramping up the MVHR etc). 

[JohnMo]

26 minutes ago, Thorfun said:

install AC

So do you use only AC for heating and cooling?

 

How do you do hot water?

[Thorfun]

Just now, JohnMo said:

So do you use only AC for heating and cooling?

 

How do you do hot water?

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.

[JamesP]

34 minutes ago, Thorfun said:

keep it simple, install AC.

@flanagaj Like you we are south facing and have no shading so do overheat.

 

I plumbed for AC in the first floor bedrooms and the main family room as seemed simplest to install. We have PV so running cost is offset and have ASHP for DHW and heating.

We cross ventilate in the evening to purge the house as @Russdl.

Would consider built in external blinds ( no view, natural light during the day) and solar glass next time.

 

 

 

Edited yesterday at 13:32 by JamesP

[Bramco]

1 hour ago, Thorfun said:

external blinds are a must. plan them now so they can be built hidden in to the fabric of the house. we use ours to shade from the sun but also as curtains at night so don't have internal curtains for privacy.

 

+1 for that - we also have external blinds on the south facing windows and no curtains.  Make sure you build in cassettes for them to go up into.

We also have overhangs on the ground floor windows but with the blinds in their horizontal position, we find that they let in the sun from the autumn through to spring which is when you want the solar gain and for the summer months, with the sun higher, they don't let any sun, so no solar gain. You can see this on our architects web site -> https://lhc.net/projects/ashcroft-creating-a-low-energy-family-home/.  In this photo, the blinds on the 1st floor bedroom are up, the blinds on the ground floor are in their horizontal setting.

[IanR]

4 hours ago, flanagaj said:

Given we are installing vertical timber cladding, these could in theory be added. without changing the appearance of the property.  Downstairs could be achieved using some sort of sun shade.

Bring down the lower edge of the cladding to the top of the ground floor windows, so you can put the top boxes for the ground floor blinds behind the cladding also:


+1 for external blinds with automated shading control.

[Alan Ambrose]

Agree with external blinds & brise soleil. Oh and low-ish g glass.

 

But also, let vegetation grow in front of the windows in the summer. It looks great and, if you choose the right plants, they love it. Then cut it back in the winter.

[flanagaj]

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

[JohnMo]

10 hours ago, JohnMo said:

internal blinds ok. UFH run in cooling mode

Mine was a zero cost option, replace blinds with curtains if you want. Choose the right ASHP it will come with cooling out the box. Mine switches from heat to cool via a repurposed light switch. So £2 if you don't have one kicking about. Runs WC for cooling and heating so you don't even need a thermostat.

 

PV - buy 2 to 4 500W panels, £68 each, string inverter £250 to £300, DC and AC isolation switch £100 for both. £100 for cable, MC4 plugs and sundry bits. Then you need mounts depending on where you locate. Panels make great fence panels, roof for pergola etc.

[SteamyTea]

12 minutes ago, JohnMo said:

Panels make great fence panels,

But greatly reduced output during the summer, if you want to use them for cooling.

This is the project for a 1kW_p system, South facing, by the sea in Penzance.

First screenshot is vertical, second is horizontal.

 

 

[-rick-]

Do you already meet Part O? If not, then heatpump driven cooling is unlikely to cut it and you need to think about what other changes to make. If you do meet Part O already and are doing UFH downstairs just set up cooling there. Upstairs if using radiators consider switching to fancoils in the same place. Pricier but probably cheaper than lots of other solutions. Adding separate A/C units in addition to your heating solution probably doesn't save you money (especially as the £7,500 from the BUS scheme might be more complicated if you plan to use it) but it's an easy option you could add in future if everything else doesn't work out. If you aren't planning UFH/heat pump heating then normal A/C units might be the easy option (but then maybe reconsider UFH).

 

As far as other changes go, dropping the cladding as per @IanR might be cheaper than brick (unless you go from being able to use a single standard length of board for each column or the extra trim around the windows is costly) so doing that you could fit 'for but not with' external blinds. Alternatively, consider planning for a wooden pergola in front of the main downstairs windows. Even if you don't do it during the build it could be a DIY job later. Of course, if not part of the build couldn't count on the solar shading for Part O.

 

Adding an overhang on the roof to provide some shading for the upper windows might also be relatively low cost but if you basically have none right now might be difficult with planning. Shrinking the height of the windows upstairs (remove from the bottom) would likely save a lot of cost and reduce heat gain. You'd lose getting sun on your feet as you stand by the window but you could likely lose up to half a metre without substantially reducing the feeling of a big window.

[JohnMo]

6 minutes ago, -rick- said:

consider planning for a wooden pergola in front of the main downstairs windows

That's a good suggestion - a pergola doesn't have to cost much. I just built one with 2x PV panels. So solar shade and generation in one assembly.

 

13 minutes ago, SteamyTea said:

1kW_p system, South facing, by the sea in Penzance.

First screenshot is vertical

Vertical just do 3x 500W panels to a 1kW inverter. Or as you say horizontal or any angle in between. It's also useful to have PV generation in winter, vertical will give twice the output in Dec/Jan.

 

A 200m² new build to a half decent build spec, should only need a 4kW heat pump. CoP of 5 to 6 doing cooling, will generally be pulling less than 500W (modulated down). If the sun's out and you need cooling, PV is generating. Our two horizontal 500W panels in full sun the other day were generating between 800 and 900W, which is enough to run our 6kW heat pump.

 

 

[-rick-]

4 minutes ago, JohnMo said:

I just built one

 

Wouldn't have thought of it if it wasn't for your thread. Very nice BTW.