Green issues concerning doors are mainly about their insulation values (for external doors) and the materials they are made from.
Good external doors are quite hard to source in the UK because we have had a poor tradition of insulating and draught proofing them. This is why eco-house builders often use the imported Scandinavian and German ones which are available here.
There are four main considerations
- The materials should be as sustainable as possible and with low embodied energythe total amount of energy it takes to make a material (or a building). See more on embodied energy – Woodmarked timber for instance.
- They should be well insulated (few UK manufacturers quote U values for doors) and it is the value of the whole doorseta complete package comprising the frame, the door, hinges, ironmongery and any other parts such as draft excluders, intumescent strips and glazing that matters. The Building RegulationsThese are the mass of regulations that cover safety, health, welfare, convenience, energy efficiency etc. in the way buildings are constructed. Not to be confused with Planning consent (which is more to do with whether you can put up the building in the first place) for doors in new dwellings come under Fabric Standards in part L1A of the Approved Documents Approved documents are detailed publications which come under the English Building Regulations. They are based on tried and tested methods of building and if you follow them you are assured of complying with the Regs. The equivalents for Scotland are the Technical HandbookUnder the Scottish Building Regulations, the Technical Handbook gives construction principles, which, if you follow them guarantee compliance with the Regulations, for Wales: the Approved documents (Wales), and for N.I. the Technical BookletsUnder the Northern Ireland Building Regulations, the Technical Booklets give construction principles, which, if you follow them guarantee compliance with the Regulations.
- They should be well draught proofed
- They should be protected from weather damage.
Obviously there are other non-ecological considerations such as appearance and security.
Doors are a great opportunity to get creative and use native, locally sourced timbers. Check out Andy’s front door.
Check that timber door suppliers are using timber with the woodmark. Some manufacturers, particularly the Scandinavian ones use a small amount of aluminium to clad the outer surface of the timber or in the form of a drip section to protect the bottoms of glazed areas. This works very well.
The U valuemeasurement of how much heat escapes (or gets in). The units are W/sq.m./°c. see Insulation properties of a solid timber unglazed doorset is about 3.0 W/m²K – quite poor, whereas composite panel doorsets can achieve values of around 0.25W/m²K. Unfortunately most door manufacturers seem unwilling to publish their U values. The building regulations cover the U values of doors and this now includes replacement external doors. Part 1LA of the Building Regulations cover this and can be downloaded as a PDF file.
Good draught proofing is essential and is now a factor in the Building Regulations section on air permeability. The problems associated with draught proofing are around endurance. They all work well at the beginning but it is very common (especially with PVC doors) to see draught proofing strips which have been accidentally torn out of place and are impossible to get back or replace with new.