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With the 2019 season now here, I've spent the last couple of weekends doing a bit of tarting up around the outside of the wee house. Little things that you don't think really matter, but the end result looks far more 'finished'. I was never very sure how to complete the gable ends of the house- whether to box them in or not- but eventually decided to kill two birds with one stone and use the space for a log store. I think it looks pretty good, and it's tempting to do the same on every side of the house, although those elevations do see a lot more wind and rain. My current obsession with processing my log pile is all down to a fantastic book I was given: 'Norwegian Wood- chopping, stacking, and drying wood the Scandinavian way'. Highly recommended, and an absorbing read even if you never intend to ever light a fire. The other bit of work has been to create a gravel path around the side of the house, and so properly edge the gravel area underneath the house. The only downside of all this work is that it makes the lumpy lawn look even worse than it did before

well, finally we have progress! after architect, (bar steward) and building control messing up warrant and having to get another which arrived friday, we are now out of the ground. the drains and tank went in at the beginning of the week and today the beam and block went down. water pipes tomorrow and soon the caravan can be connected. sooo glad to have progress.

After the rock 'n' roll plastering at the start of the month, the last 2 weeks have been all about getting stoned outside. The only drugs involved were caffeine and sugar, however, and the stone was for the perimeter drains around the house along with a few other bits. Inside, I've been busy decorating, of course, but photos of white rooms are getting a bit samey now, so they will be limited for the moment. I've been using Richard Moore Contractors for this phase of the groundworks, and they've been a pleasure to have on site. Really nice guys who know their stuff and got on with the job with a minimum of fuss and hassle. One of the big advantages for me of using a larger firm for this part of the work is their access to all their own plant and equipment - everything they needed was on hand when and where they needed it and I didn't need to organise anything for hire or delivery. A financial advantage of this is that the cost of the equipment is, effectively, free of VAT for me as everything is zero rated within the cost of the works. With a job this size, that can make a sizeable difference when compared with using non VAT registered labour only for jobs. This is at the start of the work, with trenches still being dug out and making sure the services that run around the perimeter of the garage are all staying in place. At this stage, everything was still in its post-winter boggy state, and the reduced dig left around the house was still looking like a very mucky moat. The moat was showing no sign of emptying so the guys pumped it out once they were ready to get started in there. Although the water around the house needed to go, we wanted to retain as much run-off from the roof as possible and divert this to the pond. To this end, all the guttering runs get collected into drains running around the western side of the house then to the pond via a drain that's been buried and comes out towards the top of the south tip of the pond. The outlet has been kept high where it exits to the pond to make sure that it doesn't flow back towards the house if the pond ever gets that full; there is also a decent fall on the pipe itself. This is part of the storm water drain that goes around the lounge, facing west. As well as putting the drains in, I asked the team to stone up for 1m beyond the building. This needs to be done anyway, but I also needed to get this done so that there is a firm base around the building for the next part of the team to put the stone cladding on, and also, once that's one, for the Contrasol guys to fit the brise soleil rails and fins outside the stairwell window. Here's the stoned up pathway along the front, going around to the west face. Whilst we're looking at the front door, I'm delighted to be able to post the following photo. For a few months now, the front approach to the house has been a bit on the wet side of things as the concrete that was spread there last autumn has gradually deteriorated with the lorries, vans and cars that have travelled over it on a daily basis. As well as having to walk the plank over some particularly deep puddles, the trigged up pallets and boards bridging the moat directly in front of the door was becoming increasingly perilous. Danger no more, however, as we now have solid ground in front of the building - luxury! A peep a little further around the corner shows the continuation of the path and the sewage tank going in. Prior to the tank going in, the old septic tank had been desludged - a nasty little hole in the ground that no one wanted to fall into. This was back-filled with stone and rubble then covered over when the spoil from the site was re-distributed. When we originally bought the site, the garden for the old bungalow ran to the north, parallel with the lane. The land has a slope to it going from the field down towards the lane, but there was pronounced hollow running the length of the garden that we had wanted to level out as this should make the area more useable in the winter, when there is a tendency for everything to get waterlogged. There was still some spoil left over from the pond, as well as everything that was dug out for the drains, so that was used to backfill. We have kept the topsoil that was scraped off the pond area, too, and this will be spread over the clay to give something decent to plant into. We are having an area of hardstanding next to the garage because, knowing what we're like, we will only be able to fit one car into the garage by the time we've filled it up with all the other stuff that can be put into an area like that, so we will need somewhere decent to park the cars. It's also useful for the sewage lorry to be able to pull in there and sling a hose over to the sewage treatment plant for de-sludging without blocking the lane. The guys have done a lovely job around there, and it's all nicely edged with kerb stones that flow into the edges of the driveway and down onto where it meets the lane. The amount of stone that's been put down on the site is large, over 100 tons, but then there's been a lot to do and we've also stoned up on the corner between the stairwell and the lounge where will we will form a patio of some sort. Here's a view of the hard standing going in, taken from the balcony. You can see where all the stones have been concreted in. And another taken from ground level. The hard standing merges into the driveway in front of the garage. The roadside edge of this has been increased in width by 2 kerb stones each side, on the advice of Matt, the groundworker. Besides looking better, it gives a much easier sweep up to the garage as there is quite a height difference between the garage floor and the lane, so turning in will be much easier with the more open drive. Here's the first of many lots of stone going down to build up the level. More of the same from the lane: Then with the kerb stones concreted in. And finally, with the kerbs along the lane/drive border. Everything there is ready and waiting for the final layer of tarmac, which will go down some time next week. Meanwhile, I've been doing yet more painting indoors, as previously mentioned. The large airless paint sprayer I borrowed from Jeremy is a little poorly at the moment and will be in the sprayer hospital tomorrow to have its tubes cleared out and should be back in service very shortly. I will need it again as I still have one bedroom to spray and I need the power of the large machine to reach up to the vaulted ceilings. However, I still needed to get the mists coats done on the landing, stairwell and hallway last week, as it was the ideal opportunity to get these high traffic areas done since I was the only one in the building. I was a bit stumped initially, but I had noticed the little electric sprayers in Lidl on Monday and then Weebles mentioned that they had bought one from Aldi. I figured nothing ventured, nothing gained and for £25 it was worth a shot. So I dashed down to the nearest Lidl in Blandford and got one of these little beauties. As it turned out, it was perfect for the job. The stairwell, in particular, is a little confined and with operating off a youngman board balanced between the scaffolding tower and a trestle on the landing, it would have been tricky to manoeuvre the larger machine around there. The little hand held sprayer did the job nicely and was much easier in the tight space, here: The results from the little sprayer are very different from the big airless system and you get a much more textured finish, but pleasant and perfectly acceptable. It is a pain having to refill the reservoir all the time, but not difficult. I poured the contract white into a big bucket and diluted in there, pouring into the reservoir. I confess that I didn't strain the paint and found that it was fine. The only time it gummed a bit was if I'd left it open overnight, but wherever there were any splatty spatters I just left them to dry and sanded them the day after. Sanding was quicker and less messy than straining many litres of paint. A couple of not very exciting photos of the hallway all masked up and misted: You can see from the masking you have to do that it would be tricky to get this part of the painting done if there were others working in the building at the same time. I've now put the vinyl coat on these areas too, but I was too knackered to take photos of that as I only finished them yesterday, so that morsel of excitement will have to be eagerly anticipated. I've also been painting the Howdens primed MDF doors and I'm pleased with how they turned out. I used a small fine textured roller and eggshell acrylic on top of 1 layer of white primer and very nice they look, too. Next week, Harry the carpenter (he's much too young to get all the Harry Carpenter jokes, we gave up ages ago) is back so he can get the kitchen finished off as the last of the laminate splashback arrived last week. He can also get on with some door hanging and then the utility units arrive next week. The bathrooms and loos need to be done in their entirety, the MVHR unit needs to be installed in the loft and all the plant needs to be put into the garage. For my part, I have what feels like miles of skirting and architrave to get on with, some paint snagging to do and I need to organise timings on the cladding and brise soleil. I can't think too much beyond that right now, but I know there's plenty more to do after that - isn't there always?! Stay tuned, folks!

Unlike mass which has a very precise definition (and nothing to do with heat, BTW) , if you stick an adjective thermal in front of it which means "relating to heat" have "thermal mass" a bit of an oxymoron which is a concept and without any accepted definition and can be overloaded pretty much with whatever message you want. Take the PDF that Ian originally referenced: it was authored by the Concrete Centre and has one dominant message running through it: use lots of concrete in your construction. I've modelled the thermal performance of our house in some detail. A large part of our slab is the load bearing ring and cross beams and actually plays little active roll in stabilising the house temperature; the floor slab itself does. However, the entire plasterboard throughout the fabric of the interior has just as large an effect and in terms of the overall decrement delay performance of the house by far the dominant component is the cellulosic filler used as insulation. This is because this time constant is directly related to the ratio thermal capacity / thermal conductivity, and unlike most wall fabrics which either have very poor thermal capacity or high thermal conductivity, this filler has pretty much the best combination to give good U-value performance coupled with high decrement delay. The last factor in the stability of my house is that I have relatively small window areas and no "acres of south facing glass" so don't have to cope with the solar gain tiger. So both my and Jeremy's houses have extremely low heat loss and high thermal stability, but these use a construction technique not even mentioned in the paper, and the only mention of timber frame construction is in a table on P14 where it is listed as having the worst decrement delay. So the message is: don't use TF construction if you want thermally stable construction. This shows the bias of the authors, and in the case of a Larson strut construction with cellulosic infill this is quite simple a load of bollocks.

It can be worked out from first principles if the conditions are known, but one problem is that often the conditions aren't known accurately enough to make modelling that useful. One way to try and measure it is to look at thermal admittance, which is a measure of the ability of a material to absorb and release heat into the interior of the house. However, accurately assessing this is compounded by the way that we tend to have most of the internal structure in a house (at least the part that can act as a thermal buffer) made up of layers that have widely varying thermal conductivity and specific heat/heat capacity. Plasterboard is a good example, as there is a large area of it on the inside of a house normally. It has a specific heat of around 1.09 kJ/kg.K, so for a skimmed plasterboard wall each m² will store around 10 kJ of sensible heat for a 1 degree temperature increment. Taking our house as an example, it has a total wall and ceiling area of around 600m², so the plasterboard and skim will store around 6,000 kJ, or about 1.66 kWh, of sensible heat per degree change in temperature. The plasterboard/plaster skim contributes a fair bit to the thermal buffering effect The challenge is then to try and work out how well any surface in the house will transfer heat in or out of the house. Materials with a high thermal conductivity will tend to do this more quickly than materials with low thermal conductivity. it's not much use having a quantity of high heat capacity/specific heat material in the house, but buried behind layers of material that have a low thermal conductivity.

^well said @jack

I know what you mean Ian. I'd personally prefer it if we got less bogged down complaining about the phrase itself. In my opinion, it would be more helpful to concentrate on the fact that the phrase is currently used as a shortcut to a poorly-defined concept or set of concepts. If there were a clearer definition, then the phrase itself would be perfectly fine. Indeed, since it's actually shorthand for a number of factors, I think it's useful to have a phrase that doesn't refer to any individual factor (okay, "mass" is in the phrase, but I don't have an issue with that given the context). It's a fact that the general public - and even the building trade - is never going to dig into the details of a multi-factorial heat-buffering model. All anyone cares about is whether the house or extension meets building regs. Hence, short of building regs changing, nothing is going to improve on this front - not linguistically and not practically. To be fair, the document talks repeatedly about the importance of insulation, airtightness and solar gain control over the course of the year. Page 3 even shows decrement delay in graph form (note the time offset of the damped temperature curve). Okay, they don't talk about high-decrement delay insulation, but other than here and a couple of other forums, I've never heard any self-builder or anyone in the building industry discuss the decrement delay of different insulation types. I'm sure that's at least partly because high decrement delay insulation is relatively expensive, takes up more room for a given U-value (compared to rigid insulation), is difficult to explain to the average person, and - perhaps most importantly - isn't compatible with current standard construction methods used by the big builders and most smaller builders.

Having decided to compete for business in the self-build market why would they then reduce that market size based on nothing more than a "because we can" ego trip? The original business strategy conversation would have gone like this. "Any other items on the agenda?" "Yes sir we have not decided whether to enter the self build market." Yawns around the table, people look at their watches. "Why bother it is only 0.000000001% of the mortgage market? "I am hearing rumours that big bad rival bank sees self-build as a high margin business with growth potential, look at all these TV programs". "Do we really want to be exposed to all these mixed ability self-builders, they are cranks, loonies and dreamers, I don't want us offering mortgages on tree houses like the one on grand designs the other week". "Well sir if we stipulate independent third party warranties that will filter out filter out the ex. hippie shanty town segment of self builders". "Ok we cannot let big bad rival get ahead of us, let's run a 2 year trial. Warranties only and I don't want the self build book to grow north of £50 mil during the trial".

Like all other supposed explanations for this mythical physical property, it fails because it doesn't define the units of measurement. As mentioned many times, we can measure and quantify heat capacity, thermal conductivity, decrement delay time, thermal time constant, temperature etc, but no one has yet invented any units to define thermal mass (hardly surprising as it doesn't exist as a physical property). The graph (figure 1) showing the stabilising effect is nothing to do with "thermal mass", it's just a consequence of having sufficient insulation, with a long enough decrement delay, to damp and offset the time taken for the inside of the house to change relative to changes in outside air temperature. This is aided by having a means of storing enough heat in the internal structure (and then only the first 100mm or so of it), in a layer with a reasonably high thermal conductivity, that can act as a buffer heat store.

Got to love women! ? A weekend I won't forget in a hurry. Friday night I get home and SWMBO decides "the sink would look better where the shower is"! Just the small matter of moving the window and a bit of re-tiling...Just glad I used screws not nails!

Well it was only inhabited for a few stays over winter (Christmas, New Year, and a couple of weekends in February) so I can't really make a fair comment. The only form of background heating that was left on was that the water tank- which is within the heated envelope- got a boost overnight for either half an hour or a whole hour during the coldest spells of weather. This was enough to elevate the temperature to a few degrees above ambient- I think the coldest I ever saw was around 7degC. Thanks to the MVHR there has been not even a hint of dampness, though. Our own house would never have tolerated getting that cold! When it came to heating the place back up in advance of people arriving, I would put the stove on the morning, or if I was out at work would plug in the electric oil filled radiator. Either one of these was enough to get the house back up to around 20degC by the time people checked in. I'm afraid I haven't been terrible scientific about measuring the energy input. It's a reasonably efficient building, considerably in excess of BRegs minimum, but quite a long way from passive standard. The exposed underfloor, and the small overall size (which gives a high surface area to volume ratio) count against it. It's also quite hard to justify overly thick walls in a small house, as they eat up a lot of your footprint. My walls are about 330mm total thickness and I wouldn't have wanted to go any thicker.

I hate to say this, but I opted to just cut down the trees on our site as soon as we purchased it, and before we submitted a planning application, because I had a feeling that objectors might well just get TPOs put on them in order to block us. I had a couple of complaints at the time, but there wasn't anything they could do after the event. Anyway, I've now planted 10 new trees, plus a few hundred native hedging plants, so have more than made up for the loss of a couple of horse chestnuts and a sycamore. Also, according to the EPC, our house has a CO2 "emission" rate of -0.9 tonnes/year, it's roughly the same as having about 42 trees on the site, and I doubt that 42 trees would fit.

If you had a vented cavity behind your outer skin how would that affect the temperature of the main wall construction and hence decrement delay.

Hi Guys and Gals just a quick note here to say that I am builder and have been building with Velox now for nearly 6 Years. I have used it on many new build projects, any questions please don't hesitate to ask or email me (email address removed).

No jumpers here and only one pair of socks ?

Well in that case, crack on and follow the path of least paperwork, you can submit the slate to metal roof NMA later in the build. Check out discussions here about the Nulok slate roofing system as it reduces the amount of slate substantially which should help with the revised figure you submit to the bank.

He didn’t mention the 4 pairs of socks and 7 jumpers he wears.

My one and only experience with NHBC was dire. We bought a new house (had been the show house on a small development, so was really 2 years old) and about a year later started noticing water stains on a bedroom ceiling. Investigation showed that water was getting in around the chimney breast. NHBC tried every trick in the book to get out of paying, and in the end we got our lawyer on to them. We paid for an inspection, with clear photos showing that the lead flashing had been fitted by an idiot (the overlaps were the wrong way around, believe it or not). Despite the hard evidence of the defect, NHBC still refused to sort it, and in the end our lawyer suggested that it would be cheaper for us to just get the flashing fixed ourselves, rather than continue to try and pursue NHBC. We concluded that an NHBC warrantly wasn't worth the paper it was printed on, and vowed never to have anything to do with them ever again.

I bought a very cheap Chop Saw on sale at the time from CPC for that purpose and it did great service.

For the sake of putting it in and the minimal cost compared to trying to retrofit something, I would include UFH in both floors, even if you don''t use it initially. You can at a later date set up the slab cooling for both floors. I have piped in both floors >400m2, the house is passive standard (un-certified) and you cant tell if the heating is on or not as it is so gentle (UFH flow temp of 26oC) however last summer when it was extremely hot (house just finished) the slab cooling did come on for a few days, usually in late afternoon and of you touched the floor near the manifolds you could just about tell it was cooling, but it had the desired effect in keeping the house livable.

Takes the eye off of my tiling is it's only saving grace!

Living in a static caravan is the quickest route to comprehending thermal mass, or lack of it. I liked the paper linked to by @recoveringacademicbecause it illustrates how for a given U-value the thermal mass can be varied with different building materials. Surely the combined wisdom of this forum can arrive at a definition of thermal mass. I will start: And having thought about thermal mass for 15 minutes I propose a more useful additional measure, I introduce "Effective Thermal Mass". Effective Thermal Mass = Sum( Thermal Mass over a 10 hour cooling period ).

For studding it’s fine, the tear out does not affect the structural intergrety, if it was a French polished coffee table that would be different ?. Being OCD is ok in the right place, as long as the finished product is fit for purpose (studding = strong and straight). P.s. I would only cut studding with a “fixed” saw to make sure it was square.

My house is built entirely of timber, plasterboard and insulation. The only concrete / brick is the foundations "hidden" under the insulated suspended timber floor. Yet my house takes very little to heat it, keeps it's temperature very stable, does not heat up or cool down quickly at all, and has a thermal time constant of over 13 hours. It does this (if you believe that paper) without any Thermal Mass. When they have explained that one, how my house can possibly maintain a comfortable stable temperature without lots of thermal storage capacity, I will start to take what they say seriously.

The Poor Bloody Infantry in this discussion deserve better. How - with two apparently well qualified scientists (Competent Person(s) in the lingo) taking diametrically opposite positions - can we (the people whose bank balance takes the hit) make up our minds? There will be people - many I suspect - who invest large sums of money on the basis of reading the attached paper(s). In my old jobs (running Virtual Learning Environments inside three UK Universities) I would be delighted - because I'd see the opportunity to arrange a classic Disputation (defence of a Doctoral thesis) so that students could listen and read and perhaps watch well-regarded scientists put their case. That's never going to happen here is it? More's the pity. And it's our bank balances that take the hit Is that ( ' ...that can act as a buffer heat store .... ') , J, your way of saying Thermal Mass ?

Been away for a break and just catching up on here! A bit late now but if you go to the NEC in future have a look what other shows are on at the same time time as self-build ones. This weekend there was a miniatures show on, tickets cost £8.00 bought on the day. You had to go in to get a stamp to get the car park pass so I bought the coffees and my mrs went in, got the stamp and came out again and we got our parking for £8.00 in true Buildhub style, eh @Onoff?

Mine didn’t come for sign off. Must be the same guy ?

For the conventional definition of time constants used in mathematics, physics, electronics, etc, it comes out as simply the temperature difference between inside and outside divided by the rate of change of inside temperature. E.g., if the inside of the house is at 20 °C and the outside is at 10 °C and the inside temperature drops initially (when, say, the heating is turned off) at 0.2 °C/hour then the time constant is (20 - 10)/0.2 = 50 hours. That's the length of time the temperature would take to drop to the outside temperature if it continued downwards at the same rate as it started. Actually, of course, as the temperature difference decreases the rate of cooling will also decrease so it will curve out (following an exponential curve) getting closer and closer to the outside temperature but never (in a theoretical steady-state) quite reaching it. When the temperature has dropped to 15 °C the rate of cooling should have halved so the time constant is now (15 - 10)/0.1 = 50 hours. Yipee, the time constant is constant. After the time constant it should reach 1/e ~= 0.368 times the original difference. So, after 50 hours our example house should be at 13.68 °C.

Thats fluffy dice on a Ferrari .....