The rule that matters
Approved Document L, paragraph 0.14, sets out the conditions under which a conservatory or porch is left out of the energy efficiency requirements. One of them concerns heating: the house's heating system must stay out of the room. The other conditions are ground level, a floor area of no more than 30m2, and a separating wall, door or window kept between the house and the room.
The words to hold on to are the dwelling's heating system. The test is not whether the room is warm. It is whether the system that heats the house has been taken into the conservatory. If it has, the exemption from the energy rules no longer applies, and the room is then dealt with as an extension, and the roof and walls are judged to extension standards. That is a bigger project than a few radiators.
That is why the answer to the question is a conditional yes. Heating a conservatory is permitted. What changes is the status of the room, and with it the standards the room and its roof have to meet. Our page on when a conservatory is exempt lists all of the conditions together, with the floor area limit.
Which kinds of heating extend the system
Some heating plainly extends the house system and some plainly does not. The grey area is where fixed equipment is involved.
| Heating type | Extends the house system? |
|---|---|
| Radiator on the house boiler circuit | Yes |
| Wet underfloor heating from the boiler | Yes |
| Portable plug-in heater | No, it is independent |
| Fixed electric heater on its own supply | Ask building control |
The first two take the house's own heating into the room, which is exactly what the paragraph describes. A portable heater plugged into a socket is independent of it. A fixed appliance on its own electrical supply sits in between, and since the wording concerns the heating system, the safe step is to ask your building control team before you fit it.
The Building Regulations also cover the electrical installation for a fixed heater, so the question reaches beyond heating. Ask about both together, and describe the appliance, where it will be fixed and what it connects to. A plug-in heater needs no approval at all, but a spur, a new circuit or a wall-mounted unit may. Building control will tell you where your plan falls.
What councils say, and who to ask
One council reads the rule more firmly. Dover District Council's building control page treats exempt conservatories as unheated ones, which is stricter than a plain reading of paragraph 0.14. That is Dover's own wording for its own district, so a Dover homeowner should work to it, and our page on conservatory exemptions gives the detail.
For other districts, ask the team that covers your address. Thanet runs its own building control team on 01843 577522. Folkestone & Hythe's team is on 01303 853538 between 10:00am and 4:00pm. Describe the heating you have in mind, and ask for the answer in writing so you have it when you sell. Say what the appliance is, how it is powered and whether it will be fixed to the wall or floor.
A registered building control approver can also give a view if you prefer a private route. The ruling on an individual room belongs to building control. We can say what a roof and frame will take, and what the council will want to see, and we can sit the roof question alongside the heating one so the two answers agree.
If you want a properly heated room
Some owners want the conservatory to be a normal, warm room all year. That is a different project from keeping an exempt garden room, and the roof forms part of that project.
The usual steps are:
- Decide whether the room will stay exempt or become an extension.
- If it will be heated from the house, plan it as an extension, with building control approval.
- Replace the roof with an insulated solid roof, since thin glazing and heating work against each other.
- Keep the heating controls separate, with a thermostat set for the room.
Any new roof is covered by the Building Regulations on structure, energy and ventilation, which is the standard to build to. Our page on turning a conservatory into an extension covers the change of status, and the too cold in winter page covers the cheaper steps.
For the roof itself, see conservatory roofs. Heating a room that loses heat through a thin roof is an expensive way to warm the garden. Fix the roof first and the heater has far less work to do.
