Should I buy insulated doors?

The Energy Savings From Replacing an old Door with a Composite door

In terms of energy saving I have tried to do a fairly crude calculation, but I think it comes out about right.

So a typical door is about 1.7m² (about 85cm wide by 198cm tall).

An old wooden door of this size with a u-value of 3W / m²K will typically emit about 115w of heat per hour during winter, while a composite door with a U-value of 1.8W / m²K will emit only about 70w of heat.

So that is a difference of 45watts.

If you multiply that by the hours in a day (24!) you get 1.08kWh of energy lost. This must be replaced by warm air – by firing up your gas boiler and radiators.

The cost of one kWh of gas is about £0.04, so per day you are going to be saving just over 4pence. Multiplying this by 180 days (saying for sake of argument that the winter is 6 months of the year), you would save about £7.77 a year.

Therefore to be honest the energy savings from doing this are probably not really justifiable by itself. However coupled with draught proofing benefits the savings will be significantly larger.

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Installing a new composite door could save you £8 / year
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So in my opinion, installing a composite door just for energy savings probably doesn’t justify the increased cost – however if you are going to replace it anyway – then it is certainly worth considering. If you don’t have the funds to install a new door, then I really recommend draught proofing around the frame, since this is certainly a cheap and easy way to improve the thermal properties of your home.

Reasons for Choosing an Insulated Door

Increased thermal efficiency

Whereas insulated doors have U-values of as little as 0.7, a standard solid wood door with no glazing has a typical U-value of around 3. This may be slightly lower if there is high quality double-glazing situated within the door. This high U-value would be letting heat and money escape out of your home, however insulated doors are extremely good at keeping that heat in, making sure that you have the most efficient property possible.

Increased security

Insulated doors offer amplified insulating properties of your thermal envelope, as well as improved security. With far superior stability and an increased thickness, insulated doors are proven to offer that little bit extra security helping you sleep at night.

Low maintenance

The GRP coating is really effective since it protects the wood underneath it and will not fade over time. So your new composite door will essentially be maintenance free!

Issues with Choosing Insulated Composite Doors

Glazing not encouraged!

I have always lived in a property that had external doors with glazing, and it seems like many of the UK’s population are in a similar position. However, if placed within insulated doors these panes of glass can increase the U-Value and decrease the efficiency of your door. Therefore the most efficient door is comprised of 2 sheets of steel, or carbon fibre, with a foam-filled cavity and no glazing area. When debating whether to get an insulated door, the lower the U-value tends to mean the higher the cost, however adding glazing to the door often increases the cost and decreases efficiency.

The Price

Standard doors are fairly cheap. Everybody seems to know where they stand and there are no shocks or surprises. However, when looking into insulated doors you may be stunned when you see the price. The truth of the matter is that if you are looking to get the most efficient insulated door out there, with a U-Value <2, then you are going to have to prepared yourself for a pricey surprise. That’s not even mentioning the <1 doors you can purchase at a whopping £5000.

Installing new doors

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