19 Jun 2010

Conservatories and Part L

I am still trying to get my head around the next version of Part L (the energy efficiency regs) which comes into effect in England & Wales in October this year. One of the things that looks to me to be contentious is the status of conservatories and porches.

In the last version of Part L (2006), the guidance was clear enough. It stated that if you built a conservatory outside the heated envelope, you could effectively ignore it, as far as energy efficiency measures went, as long as the thermal separation between dwelling and conservatory was constructed to a standard comparable to the rest of the external envelope of the dwelling.

This time around it’s changed. The guidance for new dwellings states this: Where conservatories and porches are installed at the same time as the construction of a new dwelling, the guidance in this document applies. The sense of this doesn’t exactly leap out at you, but you have to presume that what it is hinting at is that the whole building, including conservatories and porches, has to be treated as if it was within the thermal envelope, and that the SAP calculations have to include the conservatory (and the porch - no mention of porches in 2006). There is just one additional sentence here: For conservatories and porches added as extensions to a dwelling, see guidance in Approved Document L1B.

For those of you getting confused by these designations, Part L is split into four sections. L1A deals with new dwellings, L1B with extensions and alterations to existing dwellings, whilst L2A and L2B cover non-domestics with a simliar distinction between new and old.

So what is this guidance in L1B?

It suggests that most conservatories added as extensions will still be exempt from Part L compliance.
The exemption (from having to comply with Part L) applies only for conservatories or porches:
␣␣ which are at ground level;
␣␣ where the floor area is less than 30 m2;
␣␣ where the existing walls, doors and windows in the part of the dwelling which separates the conservatory are retained or, if removed, replaced by walls, windows and doors which meet the energy efficiency requirements; and
␣␣ where the heating system of the dwelling is not extended into the conservatory or porch.

I think that will cover 99% of conservatories and porches. So it looks as though Part L is choosing to make a distinction between how conservatories are treated in new builds as opposed to as extensions to existing homes. A new build conservatory will have to use glazing that meets WER rating of C or better, or have a U value of no more than 1.6. That means expensive double glazing at the very least, and essentially a very different beast to the basic single-glazed box you can pick up at Wickes for a few hundred quid.

So - presuming I have got this right - the question is why the difference? Surely what will happen is that people won’t build conservatories into new builds, but will wait for the house to be finalled and then go out and get what they want later. Which will result in much poorer building standards.

There is also a wider question here about who should decide where the boundaries of the thermal envelope should be. If you want an unheated room - be it conservatory, sunspace. workshop, larder or whatever you choose - why shouldn’t you be able to build one? Shouldn’t the client or their designer be able to choose just which parts of the home should be heated, and which shouldn’t?


  1. You're assuming that the government is intelligent when it comes up with these rules. Also, when it comes to real life and the huge variety of ways in which people want to run their own lives, the government never likes this and prefers to tell people how to run their lives.

  2. It's a good point. But there have been signs recently that the building regs are taking on board instances where people will simply pay lip service to them and then do what they wanted to do anyway. Specifically, the fire regs were amended to remove the requirement for self-closing fire doors on first floor bedrooms when doing a loft conversion, and the reason was simply that people fitted them and then removed them after the building inspector's final visit.

    But I fear the regs are once again shooting themselves in the foot here.

  3. Mark BennettJune 22, 2010

    While I can see how the document can be interpreted in this way I do not think that any reasonable BCO will really seek to enforce this clause as long as the building performance stands without the porch being present.

    If they do then the solution is to design the new dwelling to accomodate a porch, include as much of the structure as you can get away with at the time of the build and then finish the porch after the building is occupied. This may be as simple as fitting the door.

  4. Have to agree with you Mark, Regs are only good when the properties are built. What happens after this is anyones guess.

  5. It's simply like this because off lobbying by the conservatory industry.