Can wooden doors be as energy efficient as uPVC?
Posted by Tim Pullen on 27 June 2011 at 10:05 am
Q: I need to fit a new back door and want to make it as energy efficient as possible, but my carpenter seems a bit ignorant about what is the best way to go about this. I want to install a wooden door, not uPVC. Should I fit a sill? Or will it rot? It will sit on concrete. Or is one of those brush draught proofers as effective. What would you recommend?
A: There is a lot of talk about the comparative efficiencies of different types of doors. Timber has a relatively poor thermal efficiency compared to uPVC, but at least it is not uPVC. Timber with an insulated core is a compromise and people get very exercised about what thickness is best and the relative merits of each.
A typical external door is broadly 1.7 sq m in area. A uPVC door with a U-value of 1.8 will emit about 70W per hour of heat in the coldest months. A solid hardwood door with a U-value of 3.0 will emit 115W. It is not clear, to me at least, that it is worth putting up with all the negative aspects of uPVC for that relatively small advantage.
The door will need some assistance to stop rain and drafts getting in underneath and a sill or a rainwater-bar set in the concrete will be needed. There is no reason to suppose a sill will rot if it is properly installed.
Similarly, fitting brush draft excluders will help enormously. Even the very best timber doors are likely to move over time and a draft excluder will prevent it becoming a problem.
Photo by Laura Smart
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