Wednesday, 21 July 2021

Review: Housebuilder's Bible

Mark Brinkley's guide to building homes is a best seller and doesn't really need me to tell you how good it is. This is the 14th edition and he doesn't update it regularly only for love. However, he did ask me to check out some of the new content about low carbon heating. So I did, and while I was at it I looked at some other bits too, just because they are interesting. I can't say it is impossible to put down but it is certainly easy to keep turning the pages. I have never built or specified a house and probably never will, but if I did I would do well to start by reading this book. Actually I might want to build an extension one day and it would be useful for that. Also I have done a green retrofit (insulation) project and his section on that would have been helpful. 


What do you need from a book about house building? Well you want to be introduced to the jargon, but gently - you will need to be able to communicate with your contractors. You also need clear diagrams explaining technical things. I now know the difference between traditional strip footing and trench footings, and some of the tradeoffs between them. (Trench footings are quicker to lay and work out a little cheaper but need more concrete.) 

You need to learn how to estimate rough costs for things, working in a variety of units - cubic metres for concrete and brickwork, square metres for wall finishes, metres for drains .... Brinkley starts out by defining a model house that he uses in example calculations. Then he has tables calculating costs based on those dimensions, with alternative materials as appropriate. In fact there are lots of useful facts that can be used in your spreadsheets. How many lorry loads will be needed to carry the spoil away? A 20 tonne lorry can hold 15 m3 which works out at 12 m3 of excavated soil because it bulks up when you dig it out. Now you can do the math for your own plans.

Brinkley gives hints of what to avoid, a lot of which is about planning ahead. For example make sure you have decided on your final roof covering before you build the felt and battens layer because the batten spacing is different for different kinds of tiles. Also, if you plan for underfloor heating you can lay the pipes in the concrete floor slab. He has good advice on how to avoid condensation in roofs, which is a big issue if you have a lot of insulation at joists level because it makes the loft very cold. The solution - add ridge vents as well as venting in the eaves.

So what about the bit about low carbon heating? Heat pumps are much more common now and will be the norm as soon as gas boilers are banned (If they are banned - currently it looks like 'hydrogen ready' boilers might be acceptable). I did not like his explanation of how they work which was accurate but not so easy to understand as it could have been. I cannot fault his discussion of COP (coefficient of performance i.e. efficiency) and how to get the best out of them. He has reminded me of the possibility of skirting radiators - I wish now that we had put in underfloor heating in our retrofit ten years ago and it would be awfully expensive to do it now, but skirting radiators have some of the same advantages and are much less disruptive to install.

In the retrofit section he has made a valiant attempt at the tricky question 'Is my house heat pump ready'. The difficult bit is if your radiators will need to be upgraded. I wish I had an easy answer but I don't. Brinkley's advice is to try running the existing heating at a low temperature for a day or two. This is a sensible low-tech way to test it, though you do have to wait for conveniently cold weather (not now!). Also, you might need to increase the speed on your heating circulation pump to allow for the lower temperature drop.

There is no mention of micro-bore plumbing, which can be too narrow for the larger volumes of water you need with low temperature heat pumps. But if you do the test described above, this would show up if you have the problem. 

Brinkley has a short section on embodied carbon and energy with a table itemising the embodied carbon in the model house. The total is 45 tonnes and he usefully compares this with running a car or a couple of holidays by air. This is good but I would have liked to see the embodied carbon in alternative structures. For example, strip footings has less concrete than trench footings, but some of the volume that was concrete is replaced with brick which has even higher embodied emissions by weight - so it is not obvious which option is best for carbon overall. 

Anyway I like this book, and it is definitely headed in the right direction. 

1 comment:

  1. Thankyou Nicola for such a thoughtful review. Normally I get one liners (often throwaway ones at that) via Amazon, so it's great to get some more considered commentary. PS I also take on board useful constructive criticism and it's one of the things that keeps me producing new editions.


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