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Document L: the conservation of heat and power

Here is a link to more in depth information on document L and wood stoves

BIG CO2 emission savings can be made by heating with wood.

Changes to the Building regulations part L (conservation of fuel and power) are an effort to bring down CO2 emission rates and as such should be encouraged. They apply to new build and when you make changes to your home that need planning permission.

A notional value of the possible CO2 output of your home is calculated. This value assumes that your home adheres to, but does not exceed, current citeria that must be met such as thermal efficiency of the walls and roof, air tightness, lighting, the efficiency of the boiler, etc. We will call this the Notional Emission Rate - NER (although the document does not call it this).
So you arrive at the NER value for the kg CO2 / yr created by an imaginary house of the same size as yours. You must then ensure that your house actually emits 20% less than this value, this is known as the Target Emission Rate: TER.

The Dwelling Emission Rate (the actual calculated CO2 emissions of your home) must not exceed the TER.

This 20% reduction in CO2 emissions can be achieved in any way you want - you could add extra insulation, you could put in more efficient lighting, you could install a wood burning stove or boiler, or a combination.

You might find that your home is already below the TER - for example you may already have wood heating installed and/or very good insulation in which case no changes are necessary.

If you do need to reduce your home's CO2 emissions then you might consider installing a wood stove / boiler. The lion's share of the CO2 output of your home will be attributed to heating space and water, so installing a wood stove / boiler as either a secondary or primary heat source for space and / or water heating is perhaps the simplest way to achieve the 20% reduction in CO2 emissions.

That does not mean that you should ignore insulation - much better to have low carbon heating AND insulate well so that this heat is not wasted.

The TER calculation is as follows:

TER = C heat x fuel factor x C light x (1 - improvement factor)

C heat = the Carbon produced as a result of space and water heating (primary and secondary combined)
C light = the Carbon produced as a result of lighting Improvement factor = 0.2
Fuel factor for wood, gas, oil, coal = 1

Let's look at an actual example. The data below came from Stephen Kinsella of Kinsella Consulting -, and are the actual emission rates for a relatively large house:

Primary space heating (mains gas) 1500kg
Secondary space heating (electric) = 340kg
Water heating (mains gas) 900kg
Pumps (electricity) 73kg
Lights (electricity) 567kg

Total 3380kg CO2/yr

Based on a 90% efficient condensing boiler.

So if the owners of this home had to bring this value down by 20% - ie by 676kg CO2/yr - then they could perhaps look to reducing this figure by increasing the insulation in their house and providing primary or secondary heating using wood.
Replacing the secondary heating with a wood burner would save in the region of 300kg CO2/yr.
Providing wood primary heating would save around 1300kg CO2/yr - well in excess of the 20% needed!

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