First a bit of clarification. Some have expressed a view elsewhere that this blog is in some way a revenue-generating device for me. I can absolutely assure anyone reading it that it is the opposite. It costs me money to pay for the web space, and I don’t gain any revenue from it at all. I won’t allow advertising here, and spend a fair bit of time deleting literally hundreds of spam comments, to keep it free of commercial influence, as far as is practicable. As a consequence, whatever you read here is my personal view, and not coloured by any commercial influence. My only intention here is to hopefully try and help others, who may learn from our experience. If it saves them money, or eases their task, that that is all the reward I want.
I’ve been prompted by a discussion, following a couple of free podcast interviews I gave for House Planning Help:
to have a think about what “self-build” really means and how much money you are likely to pay out to others, even if you were to do all of the building work yourself.
All self-builders will approach their project with a different set of skills. Some may have skills and experience in building trades, some may be architects or designers, but many will be people from non-building related backgrounds who just want, for a variety of reasons, to build their own home.
The UK is a bit unusual, in that almost all new houses are built without regard for the personal needs of the person buying them. Very few people either self-build, or have a house built for them, here. Other countries, like, for example, Holland, would find us a little odd. There it is much more common for people to have a house built for them, rather than accept whatever a developer decides to build.
Another fact I found odd, was that only around 10% of UK houses are designed by an architect. I don’t know about other self-builders, but the first thing I did after we’d found a plot of land was go around to try and find an architect, as I assumed all houses were designed by architects. The fact that we struggled to find an architectural practice that were local, and competent in low energy house design, is, perhaps, not so surprising given how few houses architects actually design.
So, as a self-builder, who wants a low running cost house, should you instinctively try and find a specialist architect? My view would have to be “it depends”. If, like me, you are time rich (I’m retired) and cash poor, and if you think you can learn enough design and drawing skills (and there really aren’t a lot of drawings needed, for most house builds) then I think you can do as we did and not use an architect. Doing this is a very big cost saving. Architects typically charge between 10% and 15% of the finished build cost in fees, so we saved tens of thousands of pounds by not using one.
The flip side to that is that it meant that any design failings were going to be mine, but frankly, once you’ve signed off on an architects design you end up taking the hit on any failings anyway. This implies that you have to be knowledgeable enough at the design sign off stage to know what is good and bad about low running cost house design, which means acquiring that knowledge anyway.
Then there is the engineering and thermal design. Now this is something that is changing in the world of architecture, but quite slowly. Architects have, traditionally, been taught as art and design graduates in the main, with the emphasis on the benefits good design can bring to living spaces. No one would question the need for this, least of all me, as I found the “artistic” design elements the most challenging to get right, and I’m not really sure I did as good a job as a good architect may have done, even after spending perhaps 50 times longer on designing those elements.
Some architectural practices (and my personal experience suggests that it is the majority in the area around us) pretty much ignore the thermal design and chuck their design across to an engineer, who not only has to work out how to build the house so that it’s strong and safe, but also has to work out all the details needed to minimise heat loss, control solar gain and ensure that systems can be put in place to keep the house at a comfortable temperature, all year around.
This is where there is now a conflict between pure architecture, and the need for low energy use. Right at the start of the design process, thermal energy loss and gain must be foremost in the designers mind. If that designer is an architect, then they must understand the thermal transmission issues surrounding glazing, corners, overhangs, things like geometric cold bridging, the thermal consequences of cantilevers where steel members have to penetrate the skin of the building, along with a whole host of other, material and engineering related issues. I’ve met 13 architects now, who have visited our build. One was very definitely on the ball and someone I would trust to design and build a low energy house, the rest varied from having a little knowledge, to the majority who had the view that “all this low energy stuff is the engineer’s problem, not mine”.
There are specialist consultants who can advise you on low energy design, and can work with an architect to ensure that the design can be easily engineered to use less energy. However, most of these may try to persuade clients to adopt the certification standard of the body that approved them, and there is a substantial cost to doing that. The most common, and best recognised, low energy standard is Passivhaus, a certification standard developed around 20 years or more ago in Germany, by the Passvhaus Institut. It is a very good standard, perhaps the gold standard for low energy homes, but certification comes at a significant price.
A Passivhaus consultant may have quite reasonable fees (typically around 1 to 1.5% of the build cost) but there are a lot of additional, almost hidden costs from going down this route. The biggest, in cost terms, is that you either have to use Passivhaus Institut approved products in building the house, or provide evidence that their performance is such that they could be approved by the PHI. This can add a lot to the cost, as not unreasonably, manufacturers charge a premium for any product they have paid to put through the PHI approval process. The end result, for the self-builder, is that PHI certification can easily add 5% to the build cost in total.
Using our build as an example, here is a list, roughly in time order, of activities where we either did employ someone, or could have done, and then after it, the approximate cost savings for each item:
- Finding the plot. There are plot finding agencies, and we signed up to a couple, but generally we were very, very disappointed with what they had to offer, and the costs were high. We found our plot via a local estate agent, so incurred no commission to any plot finding agency.
- Designing the house for planning: As mentioned, I couldn’t, at the time, find an architectural practice locally who I would trust to design our house, so I spent around 6 months or more learning how to do it myself. That has now changed, and if anyone wants a recommendation for a good, local, low energy aware, architect, contact me, as I now know of one.
- Submitting the planning application: Having designed the house, I found submitting the planning application the next most challenging thing to do. Our plot had a very chequered planning history, and so my DIY planning submission needed a lot of work (listen to the first of the podcasts linked to earlier for more detail).
- Flood risk assessment: Our planners took advice from the Environment Agency and wouldn’t accept a planning application without a formal Flood Risk Assessment. I asked around, and the cost for this was going to be between £1500 and £4000. I wondered what was involved, so looked at a few that had been submitted with other planning applications and realised that I could get the data for free (it’s a combination of data from the EA and the BGS) and write my own Flood Risk Assessment. I did this in around one evening, and frankly it wasn’t a lot of work.
- Detailed house thermal design. Here I saved a great deal of time and work by choosing a timber frame and foundation system supplier that guaranteed Passivhaus levels of insulation and airtightness. They had their own structural engineer to sign the design off, which eased the Part A building regs compliance issues. I was able to look at the detail design and be assured that it was cold-bridge free and that the insulation level, and more importantly, the high decrement delay factor for the chosen wall and roof insulation, would perform as I wanted. I modelled the thermal design, initially using a fairly simple, heat loss only model (if anyone wants a copy, ask, it should run on any spreadsheet programme OK). I then put all the details into FSAP, a SAP modelling spreadsheet required for Building Regs, and finally, when I was confident that the design was close to finalised, I spent around 2 days putting all the details into the PHI thermal and energy modelling spreadsheet, PHPP. The latter is expensive, and given the small difference in output between the simple model I will let anyone have for free, combined with the solar gain and energy use parts of SAP (again available for free – contact me) I’m not convinced we needed PHPP. Our aim was to design and build a “no energy bills” house, not get any form of certification. We also wanted to save money wherever we could, and I was happy to learn new skills if doing so saved us money
- Ground works. Our plot needed a lot of ground works and this divided itself into two parts, rather naturally, the levelling of the site and the construction of a big retaining wall. The first was just digging away 900 tonnes of soil, the second a substantial retaining wall. The design of a large (~3m high x 35m long) structural retaining wall seemed to need a structural engineer. The first structural engineering company I went to wanted an initial payment of £4000, plus site visit fees of £250 per visit, plus unstated additional fees. I was a bit shocked, so sat down, read Eurocode 7, BS8002 and BS5628, then wrote a spreadsheet to do all the retaining wall design calculations. Luckily I had a soil condition report that came with the plot paperwork, so already knew the local soil and sub-soil properties. Having found it wasn’t hard to design a retaining wall, I ran into the problem that building regs and your insurance company will only accept one designed by a structural engineer who has indemnity insurance. I found a local one, we chatted, and I got an approved wall design for a very modest fee indeed. The rest of the ground works was straightforward, and needed no consultants or experts
- Submitting the Building Regulations application. Some people get their architect or project manager to do this, for a fee, typically a few hundred pounds. I looked at the drawings I’d already done, together with the drawings of the structure that MBC, our timber frame company had provided me with for approval of the design, and decided there was very little extra needed to compile a full Building Regs submission. It took me around a day of work to do one specific section drawing and tidy up some other drawings, plus add some text explaining how we were complying with the regs. Not really hard to do, and there are details of this, together with the planning application, in Part Fifteen of this blog, here: http://www.mayfly.eu/uncategorized/part-fifteen-the-site-is-finally-ready/ ).
- Managing the build. I started off thinking that I’d use a project manager (architects can also project manage builds, for around the same fee), and interviewed a few. They all said much the same, which was they would charge around 10% of the build cost to manage the build but would probably save that by getting better prices from sub-contractors. As we were only going to subcontract the electrical work and some detail work, like the larch cladding, and I was going to do the bulk of the other work there wasn’t really much scope for a project manager to save us money on sub-contractor cost. The main issue was whether or not I felt comfortable managing the sub-contractors we did use and taking responsibility for completing the house. The ground works company had managed the site for all that work, and all I’d done was a bit of over sight. MBC, the timber frame company were going to install the insulated slab foundation and erect, insulate, membrane cover and batten the house, so all that was left to manage were all the internal details, and I felt quite happy doing that.
- SAP assessment fees for building control sign off. I did all the SAP calcs, but found you have to have an assessor to lodge the paperwork – no matter how competent you are at using SAP, you cannot DIY the data base entry! I negotiated with an approved assessor, emailed my as-built FSAP calculations as a complete file, ready to be lodged on the data base and he charged me a modest fee to just put his name and number on it and lodge it for me. This still annoys me!
So, what did we save, just on external consultant/architect/project manager costs, by going down the DIY route, and how much time did it cost me to be able to make this saving?
In the order of the list above, here are the rough savings for each item:
- Between £500 and £2000, depending on the agency fee structure, say £1200.
- Around 10% of the build cost, so around £25,000
- Around £1000 to £2000 for a specialist planning consultant, say £1500
- Between £1500 and £4000, say £2800
- Around 1 to 1.5% of the build cost, so around £2500 to 3250, plus the “Passivhaus Premium” for approved matierials, which would have added another £5000 or more. In total I think we saved well over £7,000 by not going for PHI certification
- Structural engineer fees – using a local chap who knew the area and having done a lot of the base work myself, saved around £4,000 on fees
- Submitting the Building Regulations application and drawings. Typical cost around here would be about £500 to do this
- Managing the build. A project manager would have charged around 10%, and architect, as a part of a design and build contract perhaps less, maybe 5%. Not wanting to double account for savings, lets assume a saving here of £12,500
- SAP assessment fees could have been a “double whammy”, as we could have incurred fees for the Building Regs design SAP submission (which I did myself) and the final, as-built, SAP Assessment that must be lodged on the government data base. In total we saved around £200 by going down the DIY route.
Adding these savings up gives a total saving of around £54,700
This saving came at a cost in my time, though. It took me a lot more time to do all of these elements than it would have taken a professional, who already had the knowledge and experience. For example, I spent at least two weeks just learning all the building regulations, and understanding which applied. I spent even longer on learning about low energy house design and creating spreadsheets to make the calculations simpler. I spent longer again on studying domestic architecture and learning about the vernacular architecture and design for the AONB that our new house is within, and how that might be adapted to be both low energy and compliant with local planning design guidance. I also had an advantage, in that I’m a retired scientist, so both the physics and mathematics were, for me, pretty easy, and even learning the structural engineering needed to design a gravity retaining wall was only around and evenings work.
All told I think I spent around 1500 hours of my time on all the above work, plus around £50 in the cost of paper, printer ink and postage. I consider that reasonable recompense for my time, as I’m retired and on a pension, as it works out as a tax-free “income” of around £36 per hour, not a sum to be sniffed at, and a bit more than my pension pays me!
Could anyone make a self-build saving like this, on stuff where you don’t actually get your hands dirty? I’m not sure. If you have the time, a willingness to learn new skills, and a basic education up to around O level mathematics and physics, then I think it’s entirely possible.
Finally, did we succeed in our ambition, to build a “no energy bills” home? Well, the heating and hot water systems, along with everything else, have been on continuously, with the thermostats set for 20.5 deg room temperature, for over a year now. In the past week or so I received both the electricity bill (the house is all electric, there is no other form of external energy input) and the feed-in-tariff payment for the solar panels on the roof.
This was for a high energy use period (we’ve had overnight temperatures of well below freezing on several occasions) and a low electricity generation period (November is always a bad month for generation, as is December). Both the electricity bill and the FIT statement were for the same period, September 2016 to December 1016. The electricity bill was £113.10 and the FIT payment was £139.98, so we’ve over-done it a bit, and built a power station! Over the year, the house generates at least twice as much zero-CO2 energy as it uses; in a good, sunny, year probably closer to three times as much.
To conclude, I think we’ve surpassed our goal, by a significant margin. We have built a house that has cost around £1340/m² in build costs, which is around the median cost for most self-builds, we’ve exceeded our goal of building a “no energy bills” house and as a bonus we get a small, tax-free, income as being a “micro power station”, plus we have no water or sewage charges, as we’re off mains water and drainage. Sadly, we do still have to pay Council Tax, though………………….
For those interested in the daft numbers on the EPC (Energy Performance Certificate) and EIR (Environmental Impact Rating) bits of paper, then we have a final EPC of A107 (where A100 is notionally a zero energy house) and an EIR of A107, too.
The latter is interesting, as it states that the average UK house causes 6 tonnes of CO2 to be emitted to the atmosphere every year, and our house causes -0.4 tonnes of CO2 to be “absorbed”, in effect. For those into this eco stuff, our house has the same environmental impact on the atmosphere as around 40 to 50 mature trees -except we couldn’t fit that number of mature trees on the plot, so arguably it’s more beneficial for the atmosphere to build houses like this on land than to plant trees!