Getting a conservatory through building regs

[dg]

I want a conservatory with all glazed sides, but a tiled roof with rooflights. Also there will be no door to the house, only an opening.

This will not be a conservatory for buildng regs purposes, but an extension.

Now, how to I get the conservatory to pass part L (conservation of fuel and power) when the area of openings (windows and rooflights) is greater than 25% of the new floor?

Can I compensate for thermal losses by improving other parts of the house? Or will a SAP calculation be required

Cheers dg

[John Rumm]

Judging by most of the stories of conservatory construction I hear, the answer would typically be "by not submitting any kind of building notice!" ;-)

[Peter Crosland]

You will have to have a door.

Peter Crosland

[Hugo Nebula]

On 4 Aug 2005 15:30:45 -0700, a particular chimpanzee named "dg" randomly hit the keyboard and produced:

If this extension is being built against an existing wall with windows or doors in, these can be discounted (as the heat that would have been lost through them now goes into the extension). If these were single-glazed, then they can count against a proportionally larger area of 'new' glazing (i.e., if you originally had 1m² of single glazing at 4.8W/m²K, you could discount 2.4m² of glazing with a U-value of 2.0W/m²K).

You can calculate the amount of glazing for the whole house. If it's all low-e glass (with a U-value of 2.0W/m²K) and less than 25% of the floor area, then this will be sufficient. If the existing glazing has a higher average U-value, then the permissible area should be reduced proportionally.

If this doesn't work, or you're not quite there, you can increase the insulation in the walls, roof or floors. This is unlikely to compensate for the amount of glazing alone, as practically speaking, the U-values can only be lowered by one or two decimal points compared to the 1.65W/K difference between a square metre of wall and a window. Talk to your BCO. It's likely that additional measures elsewhere will help, such as increasing the amount of insulation in your existing loft, etc.

[s--p--o--n--i--x]

However, the hinges could mysteriously break at a later date and the doors removed for repair...

sponix

[Christian McArdle]

Fundamentally yes, you can. It took a rather messy and complicated court case to establish, though. Eventually, the homeowner technically lost the appeal against a decision to not grant an exemption for a similar open plan conservatory because the court believed that it was already compliant, so an exemption couldn't be granted!

However, it would be quite difficult to comply. Such an open conservatory would have considerable heat loss, which will need a lot of compensation elsewhere. You'll need to install wall and loads of loft insulation if you want to bring down the losses to below the level it was before the extension. You may get resistance from the building control department. However, the tiled roof will help you, as you can stuff loads of insulation in there.

Christian.

[Mike Harrison]

"it's not a conservatory, It's a Greenhouse....."

[Tony Bryer]

A common strategy in cases like this is to provide calculations showing the SAP Rating of the house 'as is' and as proposed, compliance being established if the proposed rating is no worse than the existing. This allows you to provide additional energy saving measures elsewhere to compensate for the extension excess heat loss. Check with your BCO to see whether he will accept this before doing all the calculations.