Light pollution mitigations

[Drellingore]

Hi folks - is anyone aware of mitigations to reduce light pollution that planners have found acceptable?

 

The National Landscapes (formerly known as Area of Outstanding Natural Beauty) management unit have raised a concern that glazing on the side of one of our proposed barn conversions may contribute excessive light pollution. The glazing is on that (west) elevation of the building as those are the views up the valley and towards the sunset; to remove the glazing would greatly reduce one of the most positive attributes of the building.

 

Some sort of timber screening is possible, but the missus isn't keen because "it will be like being in a prison". We could think about some sort of mirror film, but I don't know if the planning officer would accept this. Similarly I wonder if there's some sort of planning condition that is common and could be used, like 'turn the lights off at 9pm' or 'less than X lux Y metres from the building'.

 

Any thoughts?

 

Planning application: https://publicaccess.dover.gov.uk/online-applications/applicationDetails.do?activeTab=documents&keyVal=SEV2Q9FZGTO00

KDNLMU's comment:

Quote

In particular, we query the appropriateness of the proposed introduction of timber battens on this structure and the extent and scale of the glazing, with those proposed at first floor level of particular concern, both as an architectural feature but also in terms of potential impact on the dark night skies of the Kent Downs. It is suggested that a simpler design, such as cladding the entire building with timber (which could be applied vertically to provide a more contemporary approach) with smaller openings might be a more appropriate approach, resulting in a less ‘fussy’ design that allows the building to recede more in this sensitive setting.

 

Existing west elevation:

Proposed west elevation:

 

Location of west elevation on block plan:

Edited August 7 by Drellingore
specifying it's a barn conversion

[JohnMo]

Black out curtains. Doesn't mean you have to close them. Or even buy them, so long as they see mitigation. They need a box to tick.

 

Not sure anyone actually checks these planning conditions are implemented, once the planning stage is complete.

 

Prison bars isn't a good look or a great selling point, if you try to sell.

[Alan Ambrose]

Hmmm, sounds to me like they don't like the amount of glazing at all. They would probably prefer that you didn't have any windows ever 😒.

 

I wonder whether you could demonstrate that no-one much is likely to actually see those windows? Even a photomontage showing what it would look like from afar at night?

[JohnMo]

15 minutes ago, Alan Ambrose said:

wonder whether you could demonstrate that no-one much is likely to actually see those windows

I would be wary of going that direction, you can get answers you don't want to hear. Curtains, automatic blinds that come down as light intensity hits xx lux. Give them what they may want to hear.

[Conor]

You've way too much glazing mate.

[JohnMo]

5 minutes ago, Conor said:

You've way too much glazing mate.

Just looked at the attached drawings, I have to agree. You need a lot of mitigating measures to stop your blood boiling from the solar gain (low western sun direct into all those west facing windows), let alone the night light issue.

[Drellingore]

Ta for the thoughts folks! I don't think I, or any of you, are going to be able to convince the missus to have fewer windows on that elevation  Point taken about solar gain though.

[garrymartin]

Amazed that the planning officer isn't up in arms about the amount of glazing to be honest given it's a barn conversion. I didn't even think such a radical change with regard to window openings was allowed...

[Drellingore]

Just now, garrymartin said:

Amazed that the planning officer isn't up in arms about the amount of glazing to be honest given it's a barn conversion. I didn't even think such a radical change with regard to window openings was allowed...

 

Aye, it's a fair point. This barn is however a secondary concern to the non-designated heritage asset 18th century threshing barn next to it though, so we've been a little more liberal with this, as it's currently a concrete-and-asbestos monstrosity with no public views of that elevation.

[garrymartin]

Perhaps worth reminding your wife that glazing below 850mm doesn't aid views or daylight much, and ends up costing more... 😉 

 

Do you need three sets of sliders? Would reducing the overall height of some of the openings put the National Landscapes chappie more at rest without diminishing the views you cherish or requiring other conditions?

[Alan Ambrose]

>>> it's currently a concrete-and-asbestos monstrosity with no public views of that elevation

 

Ah, a valuable heritage asset built with authentic materials which needs preserving at all cost... 😀 - I've completely lost it with the planners at this point.

 

Our current barn conversion was worthless (I paraphrase) to the heritage people and could be knocked down as far as they were concerned as they didn't care. Now they're all about preserving its barn-like qualities...

[ChrisInKent]

Even if you get this glazing through planning approval you should get a quick check done against Part O Building Regs compliance for overheating calculations. We had to revise our plans because the overheating calcs meant we couldn’t reach compliance - and we had way less glazing than on your design. Mitigation might be through cross ventilation (on opposite sides of the room) or external shading or the other- have a look at the link. It doesn't look like either have been designed in your house yet.

 

Once you get the changes agreed you then have to do a material or non material amendment to the LA, it’s a few 100 pounds each time. 

 

https://www.futurehomes.org.uk/avoid-overheating

[Drellingore]

Thanks! All good suggestions. We'll probably dig into the overheating concerns in the detailed design phase if planning approval is forthcoming.

[Adsibob]

1 hour ago, Drellingore said:

We'll probably dig into the overheating concerns in the detailed design phase if planning approval is forthcoming.

Sorry but this is really quite naive. Solar gain is a very serious problem and not something you can easily address after you’ve got planning without actually making an amendment application.

 

Your western wall looks, and will behave like, a greenhouse. I would reduce the amount of sliders on the ground floor, and make the windows on the first floor much smaller. You will still be able to appreciate amazing views. 
 

Regarding the ground floor sliders, you could instead make some of them out of timber or steel, rather than glass, and go with an industrial look to match the barn’s heritage. In that way, when they are closed there is no light pollution, but when open you get the views. Alternatively, cover the glass with sliding wooden external shutters. You will appreciate this when the house overheats.

Edited August 7 by Adsibob

[dpmiller]

what is the manner of the expected light pollution- out over the countryside or reflecting upwards off the hardstanding in front of the glazing? Dark Skies is all about upwards emission AFAIK.

 

might there be some merit to an overhang/ brise soleil in terms of solar gain but also upwards transmission?

[Alan Ambrose]

Re solar gain. +1 to getting some up-front calcs. Fill in the simple part O spreadsheet and see how far you’re over.

Even simpler is a window to floor area calc to see if you’re in the right ballpark, see e.g.:

 

https://sustainableengineering.co.nz/glazing-percentage-handy-rule-of-thumb-to-prevent-overheating/#:~:text=Prevent overheating by keeping the,found it holds true there.
 

Options later are simple part O (if you’re not far over), PHPP shading calcs if your BC will allow it (my LPA BC won’t, but a private local BC has said it would) or TM59 if you want to push the boat out. The last two allow the effects of brise soleil, external shutters/blinds, low g glass, reveals, shading from trees etc to be taken into account. The simple part O calc won’t allow adjustment for any of those.

My strategy is to get planning permission with a high glass content and dial back with a non-material amendment if needed. In the meantime I’ve done detailed PHPP shading calcs and determined that I can control the gain with external blinds on the W & E windows (I have v few S facing). That’ll probably need to be verified/repeated by a qualified PHPP person to convince BC.

In my view the whole part O thing should never have been applied to single dwellings. The whole part O rational was driven by modern London flats getting hot during Covid. The big housebuilders had their fingers on the creation of the part O rules, so they wrote the rules to suit themselves. Also, you can mitigate after the fact fairly easily with a detached house with awnings etc. You can’t do anything much with a flat, particularly if you’re renting. 

[Adsibob]

3 hours ago, Alan Ambrose said:

you can mitigate after the fact fairly easily with a detached house with awnings etc.

This assumes you aren't being charged an arm and a leg for having to erect scaffolding. I wanted to install some external smart brise soleils, made with microfins. Really impressive product and was happy to pay the £500 or so for the product itself and the £180 for installation. But then the installer quoted an additional £1400 for the scaffolding and I said no thank you. I think I'm regretting it now as my loft floor office gets hot

Edited August 8 by Adsibob

[Alan Ambrose]

These are on the 2nd floor and, say, powder coated aluminium? Unless, they're massive, I would of thought they could be installed from a tower.

[Adsibob]

7 minutes ago, Alan Ambrose said:

These are on the 2nd floor and, say, powder coated aluminium? Unless, they're massive, I would of thought they could be installed from a tower.

Yes, I think the issue is that the tower needs to be mounted on a sloping roof that is above the ground floor extension. I thought that would make it easier, as it's less height to erect, but apparently the slope makes it more "technical".

[Conor]

16 hours ago, Drellingore said:

Thanks! All good suggestions. We'll probably dig into the overheating concerns in the detailed design phase if planning approval is forthcoming.

 

You need to do this now, as you might not be able to add shutters / shades without putting in a new application as it's unlikely to be a non material change. Also your initial SAP. That amount of glazing could be a fail for overall fabric heat loss. I'd go back to the planners and say you are going to address the comments and come back with an amended design. We needed a 6x2m brise soleil that was contentious with the planners and needed some other design changes to accommodate.

Edited August 8 by Conor