Do all windows have to be 1100mm from the floor to opening now?

[Papillon]

part O, section 3.8

 

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1057374/ADO.pdf

 

 

I just noticed a part in the new part O requiring 1100mm as windows are now supposed to be open all the time due to it being warmer.  This is more of a balcony height rather than a typical window height which is about 900mm.
 

I’m a bit confused how it works.

 

If true, windows will feel too high and look squashed in proportion. Imagine every window like a bathroom window.

Now obviously sash windows are a bit of a problem. The proportions of a Georgian-style house will look pretty bad.

 

I’ve no idea how this works with fire escape windows, since that’s the maximum height. If you can’t use fire escape windows then you can’t have open plan stairs.

 

Plus the guarding has to be non-claimable so can’t be a bar right?
 

Do you think it will apply on the ground floor? It doesn’t say it won’t. Is it  all windows or just windows used for air flow? Does that mean if you have passive ventilation it doesn’t matter?

 

Has anyone had any experience with this yet. 

Edited June 30, 2023 by Papillon

[Sparrowhawk]

14 minutes ago, Papillon said:

Now obviously sash windows are a bit of a problem. The proportions of a Georgian-style house will look pretty bad.

According to a recent Twitter discussion having the sash open at the top only is one way to address this

 

[Papillon]

Ooh that’s interesting, good find! Seems like downstairs too.

 

I haven’t worked it out yet, I guess the split would not be in the middle of the sash.

 

I usually do windows 2100mm from the floor, 1200mm high. 
 

maybe the solution is to also move the windows up, and maybe the ceiling too? Higher ceilings are nice. Sorry for short people who can’t see out the windows though.

[MikeGrahamT21]

I'm going to assume along the lines of the other building regulations, and obviously speak to BCO about this, usually you can do whatever you want to (in terms of energy efficiency, and in this case overheating) if you do something along side it to mitigate any ill effects which it could cause, so perhaps some kind of external shading to mitigate the increased heat ingress, and ventilation will help with this. I would assume fire escape regulations would take priority.

Have heard other people having to do dynamic thermal modelling (or rather having it done for them) to prove what they are doing won't suffer from overheating.

Luckily all my builds came before this was introduced, its certainly complex and adds a lot of cost to a build

[Glenn]

Hitting the news https://www.thetimes.co.uk/article/ditch-barmy-windows-rule-that-makes-new-homes-darker-ministers-urged-w8mld79j5

[Temp]

We made a mistake and our upstairs windows were slightly too low. BCO allowed them provided we fitted restrictors. Would have cost a fortune to change due to the design.

[Alan Ambrose]

>>> I usually do windows 2100mm from the floor, 1200mm high. 

 

More skylights than windows then?

[Dave Jones]

1100 is fire regs. can ignore for ground floor windows exiting onto a hallway to outside door. Everyhting else has to meet 1100 and have a 450 clear opening so a 500 sash.

[kandgmitchell]

This bit of Part O is madness. Suddenly just because the weather is getting warmer we may be at greater risk of falling out a window that has been left open! It does say "falls from height" so I'd argue that wouldn't apply to ground floor windows. It's certainly challenging if you need to combine both means of escape with a window needed to reduce potential overheating in an upstairs bedroom........... 

[Nickfromwales]

3 hours ago, kandgmitchell said:

It's certainly challenging if you need to combine both means of escape with a window needed to reduce potential overheating in an upstairs bedroom........... 

You could have "normal" sized windows in a certified PH, and apply solar reflective coating to manage that. The PH architect would likely push back, but so would then I.

Sense would of course prevail.....

[Dan F]

10 minutes ago, Nickfromwales said:

You could have "normal" sized windows in a certified PH, and apply solar reflective coating to manage that. The PH architect would likely push back, but so would then I.

Sense would of course prevail.....

 

Overhangs and blinds are the best first measure to manage overheating from solar gain, before using reflective coatings or reducing window sizes.  Correctly designed overhangs allow light in the winter, but shade in the summer and blinds of course and be used on demand.

 

Depending on u-value and g value of your windows, smaller windows can actually increase the yearly heat demand of a building, due to a reduction in solar gain in the winter (when overhangs don't shade as much and blinds are up).

 

Edited July 5, 2023 by Dan F

[Nickfromwales]

10 hours ago, Dan F said:

Overhangs and blinds are the best first measure to manage overheating from solar gain, before using reflective coatings or reducing window sizes.  Correctly designed overhangs allow light in the winter, but shade in the summer and blinds of course and be used on demand.

Indeed, and I've just had this exact conversation with the PH architects on one of my current projects. I'ts down to whether this was impactful on the front facade or not, but blinds (external) would always be my 1st choice for ground floor at least. Overhangs can be a design feature and integrated early at the design stage, so both shoes fit tbh.

The main point is, I dislike anything dictating window sizes when PHPP can be manipulated (rob Peter to pay Paul) to achieve a mutually beneficial outcome (manage 'issues' / retain larger windows to enjoy southern views etc), and I feel that PH often focusses too intensely on the dwelling and not so much on the occupants, who may be in residence for multiples of decades. The focus of my attention is always "client first", and then we look what issues that has created and then I 'engineer' my way out.   

[Temp]

From what I can see...

 

ADK (Protection from Falling) - Min height of windows 800mm.  

ADB (Escape from Fire) - Max height 1.1m of escape windows.

ADO (Overheating) - No max/min but to count towards your overheating mitigation strategy any window that opens more than 100mm must have guarding to 1.1m and meet other rules in para 3.9.

 

So you can still have 800mm high openers if you fit 100mm restrictors.  

 

[Temp]

22 hours ago, kandgmitchell said:

so I'd argue that wouldn't apply to ground floor windows.

 

It only applies to ground floor windows where there is a height difference of more than 600mm between inside and outside. See table 3.1.

 

[DevilDamo]

And it only applies to new dwellings.

[Iceverge]

How much of this regulation is based on  data rather than hunches? 

 

Our kids just fine a suitable box/chair to climb up on what ever height they fancy. 

 

Having higher window sills make zero difference in our case other than increase the fall risk back into the room when they invariably find their way up on the sill. 

 

 

[DevilDamo]

10 hours ago, Iceverge said:

How much of this regulation is based on  data rather than hunches? 

 

Our kids just fine a suitable box/chair to climb up on what ever height they fancy. 

 

Having higher window sills make zero difference in our case other than increase the fall risk back into the room when they invariably find their way up on the sill. 

 

 

You could apply the same logic to many different regulations. If there was a fire in a room and your cills were over 1100mm high, you’d be damn sure to make sure you get yourself out of that window.

[kandgmitchell]

On 06/07/2023 at 17:21, Temp said:

It only applies to ground floor windows where there is a height difference of more than 600mm between inside and outside. See table 3.1.

It's a pretty rare ground floor window where the floor level inside is 600mm + above the external ground level. So normally the requirements of part K apply which says you need guarding if a person can fall more than 600mm. So, if your floor level is say 200mm off the external ground level then the cill height of a window can be at any level as you cannot fall more than 600mm.....

 

If you want to keep to 800mm high cill heights at first floor level, restrictors will only work if the openable area with them in place meets the requirements of the openable area needed. Otherwise guarding will be needed.

[Temp]

9 minutes ago, kandgmitchell said:

It's a pretty rare ground floor window where the floor level inside is 600mm + above the external ground level. 

 

I suspect its more common than you think. Our house is on a slope so the inside is on three levels. I just realised one of our windows that looks down the slope is caught by this. Good job the BCO didn't spot it when built in 2007.

 

 

Edited July 15, 2023 by Temp