Shutters? Do we need them?

[puntloos]

So the common knowledge is that shutters help against (fix?) solar gain - sun shining inside and heating up surfaces. Especially helpful when people choose to have lots of glass. 

 

But, with passivhaus, I get the impression that PHPP and passivhaus advisors are somewhat fine with not putting external shutters on windows. Can someone explain the reasoning there? Are they relying on the fact that UK sun only comes out 3x per year or can the house (perhaps ASHP in cooling mode) deal with solar gain as long as it's not too much glass?

 

To put the question very differently, I have 5 velux rooflights (1 morning sun, 2 afternoon sun facing, 2 north facing) and currently they don't have shutters. The top floor doesn't have heating/cooling in the current plan.. so it feels like I should add shutters at least to the sunfacing ones? 500 quid per shutter starts to add up..

[Conor]

I don't think so. As I've posted before, add up all the costs of the shuttering shading and convert that to electric use for ASHP cooling. For us it was like £6k, which translates to several hundred days of (PV assisted) cooling. Works really well for us*

 

 

 

*Being in northern Ireland, hottest we've experienced is 27-30c for about a week. When we were running the ashp for cooling, we were still exporting PV overall, so I'm assuming cost is nominal.

[Dan F]

10 minutes ago, puntloos said:

But, with passivhaus, I get the impression that PHPP and passivhaus advisors are somewhat fine with not putting external shutters on windows. Can someone explain the reasoning there? Are they relying on the fact that UK sun only comes out 3x per year or can the house (perhaps ASHP in cooling mode) deal with solar gain as long as it's not too much glass?

 

I wouldn't agree with that. It's going to be dependent on the specific house design, size of windows and orientation, but PHPP consultants are generally going to want to use overhangs/shading as the primary way to reduce overheating (most people don't want to make their windows smaller!) and they try to avoid the need for active cooling (at least in the U.K.).

 

Do you have a PHPP model for your build? That's the best way to understand the impact of these Velux having (or not having) shading.

 

 

Edited March 9, 2023 by Dan F

[puntloos]

31 minutes ago, Dan F said:

 

I wouldn't agree with that. It's going to be dependent on the specific house design, size of windows and orientation, but PHPP consultants are generally going to want to use overhangs/shading as the primary way to reduce overheating (most people don't want to make their windows smaller!) and they try to avoid the need for active cooling (at least in the U.K.).

Fair. I might have to go ahead with them then.

31 minutes ago, Dan F said:

Do you have a PHPP model for your build? That's the best way to understand the impact of these Velux having (or not having) shading.

 

There is a model but it's not in my hand. My architect/contractor have it.

 

[Dan F]

3 hours ago, puntloos said:

There is a model but it's not in my hand. My architect/contractor have it.

See if you can get hold of it.  It's really easy to add/remove shading. It's also easy to stress-tests by reducing max comfort temp down from 25C or changing climate data.

[Russdl]

What @Dan F said.
 

Get hold of it and tweak it to see what works best.
 

For what it’s worth, the few sunny days we had recently had us warming up a treat, it wouldn’t take many sunny winter days for us to consider lowering an external blind or two.