Part Nineteen – Sorting Out Details

This nineteenth entry was published originally by JSHarris on the 21st October 2013 and received 1,645 views on the closed forum

Now the house is up, the roof on, felted and battened, I’m chasing around sorting out some of the details. Despite having planned this build for the past couple of years, and thinking that I had every detail pinned down, I’ve found that in reality there is a lot of stuff you can’t really decide on for sure until the house is up.

As far as the main build goes, the windows should go in this Friday (and the Munster Joinery chap has been on site to check the aperture sizes and reckons there shouldn’t be any problems), the in-roof solar panels go on this Saturday (25 of them, covering about 43m² of the south facing roof elevation) and at long last the fence between us and the neighbour’s garden should go in tomorrow (weather permitting). More on the fence saga later.

We’d settled on an in-roof photovoltaic panel system a long time ago, but struggled to find a supplier with expertise and experience in fitting them. It seemed daft to fit PV panels over the top of slates, plus, no matter how good the installation they always tend to look a bit like a carbuncle on an otherwise attractive looking roof. There’s also the issue of the waste of slate – why put expensive slate under a weatherproof array of PV panels? Initially we settled on using the Easy Roof system, made by French firm IRFTS. However, when it came to it they seem unable to supply on time, so we’ve gone for an alternative (also French) the GSE Integration system. Essentially this is a series of flashing trays, with built in panel mounts, that fit directly to the roof battens. One advantage of this system is that we can fit the PV panels right at the eaves level with the lower flashing going to the gutter. This avoids having a couple of courses of cut-down slates along the lower edge, which may have been prone to wind lift. The PV panel supplier have been pretty good so far, but they have made me think a bit about the order in which we do things. For example, the consumer unit would normally go in at second fix, after the plasterboard is in. However, the PV wiring is best put in at first fix, and this needs to be terminated to the consumer unit. The compromise is that I’ll fit an OSB panel for the consumer unit and extended tails from the outside meter at first fix, and then fit plasterboard around this. As this will be inside a cupboard the bit of OSB showing won’t matter, in fact it might make fixing some of the other stuff in this utility area easier.

One problem we’ve had is with the fencing contractor. We contracted for the fencing that should go on top of the retaining wall, and which forms the boundary with our neighbour, over two months ago. At the time we explained that it was an urgent job, as there was a serious safety hazard presented by the 2.5m sheer drop down to our garden from the neighbours garden. We signed a contract and agreed a price, and paid up front for some of the materials. However, since then we’ve been given the run around. Dates for doing the work have come and gone, the most recent being a promise that the guys would be on site at 08:30 last Friday. I arrived bright and early on Friday morning, hung around for an hour and then got a call from the fencing firm saying that they wouldn’t be coming as a chap had just phoned in sick that morning. At the time I thought this was fair enough, but a bit of a nuisance. Anyway, this morning I was back on site first thing, and got a call from a fencing sub-contractor who wanted a site meeting. We met, had a chat about the job and it turns out that he had been sub-contracted to do this job for the past month. I asked why he didn’t show on Friday. He said he was only asked to call me today about doing a site survey for the job. Apparently the yarn I’d been spun on Friday about a chap calling in sick was a load of rubbish.

Anyway, the good news is that the sub-contractor seems a good bloke (I’m getting a feel now for the bullshitters!) and he’s going to do the sub-contract work for the main fencing contractor as agreed. I had mentioned to the main fencing contractor that there would be some extra work needed that we’d decide on-site on the day and cost as we went along, after a discussion as to the best way to tackle it. Now I’m going to only pay the main contractor for the exact work that we’ve contracted and I’ll separately agree a price for the extras direct with the subbie. The really stupid thing here, from the main fencing contractors point of view, is that we have loads of other fencing and hedging to do on site, and he’s now put himself well out of contention for that work. If the subbie does a good job on the neighbours fencing then I’ll hire him directly for all the other work we need. I’m frankly amazed as to how some of these firms stay in business, as this is far from the first one I’ve found that can’t be bothered. The contrast with the excellent response and work from some of the other firms I’ve dealt with, especially the Irish companies like MBC Timberframe, etc, is stark. The only UK firms that have been similarly responsive and done a good job were the ground works guys, Digging It, the excellent brickie we used, Chris Coward and the very good renderer, Rafe Gulliver. I’m building up a list of those people who I’d use again and a much longer list of those I’d not bother with, so if anyone is looking for trades people in this area let me know and I may be able to advise on some of the good guys we’ve used.

The other bit of news at the moment is that, at long last we have running water on site. The borehole turned into a massive tale of woe, both because of the site geology and because of unforeseeable equipment breakdowns. Despite the truly evil weather today the chaps from Geologic Boreholes came and put our well head in place and dropped the pump down the hole. The test pump gave a yield of 1,369 litres per hour, with the level of water in the hole stable at 13.84m down from the top whilst it was being pumped. The hole itself is 70m deep. So, it looks like we have a healthy supply of water, as we only need around 300 litres or so per day. The pump can deliver around 22 litres a minute, which combined with the storage in the pressurised buffer tank we’re putting in should be fine. Despite all the problems we had with the borehole, I’d strongly recommend Geologic. None of the problems we had were of their making, and their guys battled through some pretty grim conditions to get this hole drilled for us, on a firm price contract, too.

I’ll be glad to get the doors and windows in to get the house properly weather tight, as the weather has very definitely turned over the past few days. Once the solar panels and slates are on and the doors and windows in we should be completely water tight, and can start the internal fit out, some of which I’ve decided to do myself. We’ve changed our minds on the MVHR, as we were going to fit the Genvex Premium unit, with a built in air to air heat pump. This would have provided a bit of extra air heating and a bit of comfort cooling in summer, but we’ve decided that the price is just too high. It’s more than five times the cost of an equivalent performance MVHR, and the cost of the genvex ducting alone would cover the cost of the Titon HRV 2 Q Plus and radial ducting system. The ducting arrives tomorrow and I’ll probably make a start on fitting it in the floor joists. The system I’ve opted for looks very easy to fit, promises to be low noise by virtue of it’s radial design and should offer low flow resistance, again because of the radial design. The same ducting system seems to be available under different names. Polypipe sell it under their Domus brand, but the stuff seems to actually be made by Brink, as their HB2 system. It’s the latter we’ve bought, from a firm called CVC. The ducting has come to around £1k (including all terminals, manifolds, external duct etc) and the MVHR is about £1.1k, so MVHR and ducting has come in around £2.1k, which is around £6.2k cheaper than the Genvex system (excluding labour).

I’ve bought myself a second hand air flow and temperature meter for £30 to set the MVHR up, as I can’t see why I need to pay £300 to have this done. It remains to be seen whether the BCO will accept my air flow measurements and report as being compliant with Part F!

The final detail decision this week has been on the heat pump. I’ve been pondering this for ages and have finally settled on a pump that will be a bit of an overkill, but which wins by being easy to install and having a good reputation. It’s also pretty reasonably priced at around £2k. The plan is to fit a 6kW Panasonic Aquarea monobloc unit, fitted to the rear wall of the house. This will feed a 60 litre well-insulated buffer tank just the other side of the wall, inside the utility room. The buffer tank will be heated to around 35 to 40 deg C by the heat pump. The underfloor heating will feed from the buffer tank, with thermostatic mixer valves controlling the UFH flow temperature (which I expect to be around 24 to 26 deg C – it’s a very low temperature system). The buffer tank will also have a thermosyphon feed vertically up to a thermal store immediately above it in the first floor services space. This will be a non-pressurised thermal store, filled with antifreeze mixture (to protect the monobloc heat pump) and will have an immersion heater to increase the preheated store temperature from around 35 deg C to around 60 to 70 deg C. The electricity for this immersion will normally come from excess generated power from the 6.25 kWp PV array (via a diverter, like the Immersun unit), but on very gloomy days it will use a bit of grid power to get up to temperature. The plan of the system is below. The power diverter over ride switch will probably be a time switch set to come on after dark, to charge the thermal store up if it’s been a dull day. Domestic hot water will be at “mains” pressure via a heat exchanger coil in the thermal store.

[EDIT – NOTE THIS SYSTEM WAS CHANGED – SEE LATER BLOG ENTRIES FOR FINAL SYSTEM]

Overall this system won’t use any more power than we generate through the year, so will have a zero running cost. In fact, because of the Feed In Tariff payment we’ll actually generate an income through the year as a whole, so won’t have any utility bills at all. The only bill we can’t avoid is Council Tax, as I can’t see a way of getting out of that one………………

Sorry for the lack of photos in this entry, the combination of nasty weather and the build looking much the same as it did at the end of last week has meant I’ve not taken any for a few days. I do have a time lapse camera set up on a pole overlooking the site, though, so if it’s worked as planned I should be able to put together a video of the house going up in a few minutes when we’ve finished.

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ProDave 21 Oct 2013 06:11 PM :

 A question about the in roof solar PV panels:

I can see in principle it’s a good idea.

but my little brain box can’t help wondering two things:

Firstly it’s on your front roof with a little gable end for the porch. so you don’t really want the panels right down to the gutter level, otherwise you will get some shading from the porch gable at the ends of the day. so better to keep the panels higher up?

And secondly, unless you have designed your house around the size of standard solar panels, then there will no doubt be some bits of roof to fill in around the edges of the block of panels. What do they use for that? standard slate, or something made to look like PV panels, so you get a truly even looking roof all over?

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jsharris 21 Oct 2013 06:29 PM :

 ‘Tis a challenge to get the panels to fit without appreciable shading, that’s for sure! What I’ve done is leave a big space around the gable that will be slated, and there will be slates up the sides and across the top of the array. There’s no way around this with the products that are presently available, as none of them allow going right to the verge side of a roof, although they will accept going right down to the eaves or up to the ridge slate/tile.

They don’t look too bad with slates around the edge, though, certainly neater than being on top of slates. Here’s a photo of how the system looks: http://www.saveenerg…/easy-roof.html

The slates around the edge are cut in just as they would be around a Velux window, in fact the panel flashing kits are very similar to those used for roof windows.

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Alphonsox  21 Oct 2013 07:26 PM :

 Once again many thanks for sharing this level of detail – it is really helping to focus my thoughts for our own design.

You have previously mentioned the Venta Axia Kinetic as a possible MVHR system. What made you choose the Titon instead ?

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 jsharris 21 Oct 2013 08:20 PM :

 Thanks for the kind words, they are much appreciated.

The choice of MVHR was not at all easy. I started off looking at the heat exchanger efficiency, thinking that more efficient = better. This turned out to be a false comparison. Next I looked at comparing the specific fan power (SFP) which tells you how much power any given MVHR needs to move a given volume of air. Again, this is a false comparison technique.

In the end I looked at the operating point that our MVHR would be working at most of the time (an air change rate of around 0.45 times the house volume per hour) then looked at the efficiency and fan power that a range of MVHR units would give. I picked the HRV 2 Q Plus over the slightly smaller HRV 1.75 Q Plus because it would work efficiently over a wider range of duct back pressures, and despite the headline SFP figures for the two, the HRV 2 Q Plus actually has a better SFP at our typical 154 cu m per hour ventilation rate.

The final clincher was the price, £1140 supply only, which seemed quite reasonable.

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 ProDave  22 Oct 2013 07:28 AM :

 Are you going for the renewable heat initiative payment (which demands install by an MCS installer) or are you not bothering?

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 jsharris 22 Oct 2013 07:40 AM:

 I haven’t decided yet. It’ll be a trade off between the much higher price I’d have to pay to get the ASHP installed by an MCS firm and the benefit we’ll get from RHI. Early indications are that the price of this ASHP via an MCS installer would be a bit more than double the price of me just buying it and fitting it myself, pretty typical really, as all these government schemes seem to be focussed on job creation and profiteering, rather than consumer benefit.

The PV system is being installed by an MCS firm, I’ve just resigned myself to paying around £3k more than I have to for the system, as in that case the FIT payments will cover the MCS installation premium within a couple of years. I do think it’s crazy that we have to pay such a high premium to get a bit of paper that’s needed to get the subsidy, but there doesn’t seem to be a way around it. In the case of the roof system I suspect I’m paying around £1000 per day for two chaps labour and a certificate – nice work if you can get it!

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 ProDave 22 Oct 2013 08:06 AM :

 The house I mentioned that I wired recently, the system was supplied by a local MCS registered company. They were happy to let “the builder” install it, and they just came and comissioned and set up the heat pump. This should get it’s MCS certificate and qualify.

When the time comes I’ll approach them and see what they can offer me, but I have to say I’m not impressed with exactly what they specified for that system so would want more input in the design of it.

The RHI payment is only for 7 years, a LOT shorter than the Solar PV FIT contract of 20 years. That also needs to be taken into consideration to see if it’s worthwhile paying extra and jumping through hoops for a relatively short lived payment.

As with most things, since you are way ahead of me, you will be doing the sums first so I will be interested to see what you find.

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jsharris 22 Oct 2013 08:20 AM :

 That’s a good tip, Dave, I may see if the MCS firm I’m using for the roof will do the same and just charge me for commissioning, providing they are able to supply the unit I want at a reasonable price. I’m opting for a monobloc because it’s dead easy to fit, just flow and return water pipes and a power cable, couldn’t be easier really and no messing around with refrigerant pipes and gas. The downside is the need to run antifreeze in the primary circuit (in case of a power cut) and the need to insulate the flow and return pipes very well (easy for me as it will be up against the back wall of the house, right behind where the buffer tank will be).

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