davidc

Thanks folks, it was really the question of how the Fir might perform versus the Larch option (i.e. splitting, bowing, fungal growth etc) in the first place that I'm wondering about most of all.

I have a couple of large Douglas Fir that need clearing from my self-build plot, I am wondering if it maybe worthwhile considering using them for exterior cladding (for main dwelling not outbuildings) if I can get them milled - does anyone have any knowledge regarding that ? I believe Siberian Larch would be better, at least if it was available, but I'm trying to gauge how inferior non-plantation Douglas Fir might be. Does Douglas Fir require pressurised preservative treatment that leaves it with an orange hue ? Thanks

Thanks, @Thedreamer and @Iceverge . I did consider an EAHP but concluded that the air flow rates required (as air has a much lower heat capacity than water) were likely to present some challenges in an air tight home with MVHR. I'm starting to regress back to the mean position of, if a having an WBS, just having it for space heating but the issues surrounding <2kw output, particulate leakage and knowing that the installation and stove itself won't make a sizeable dint in the airtightness remain !

@jamieledI'm starting to think the only way I can do it well with a WBS and TS is the Tonwerk route which put about 1.3 kW to the room and approximately the same to water but at cost of ~£10k for the stove if my currency conversion is right, seems to me, like the tail would be wagging the dog in the sense I'd be spending a fair bit of extra cash just to save some cash. @PeterW that is all new to me, thanks, the house is only 125 sq. m and the budget is fairly modest so perhaps going down that route I'd end up in the same position as above in terms exploiting the free fuel but adding to the build costs a fair bit ? I did think about trying to find out if there was any mileage in getting a pellet maker and seeing if a pellet burning stove would change anything. I may just end up having to have a WBS as secondary heat source - if I can find one with low enough output that is and a better understanding of the supposed problem of indoor particulates and which models mitigate that best.

Several Woodfire models have that split so it may have been one. They aren't DIBt I believe. I'm also trying to accommodate countervailing requirements here as as I'd also like to keep the house as cool as possible over the warmest months - which I think a TS may hamper.

@JohnMo thanks, I didn't have that on my list but it may have a tad greater output that I'd like - hopefully less than 2kW to room The benefit, as I see it, lies in the fact I have unlimited Scots Pine within 200m of the plot and if possible I'd like to use this to provide some of the DHW and heat, the latter (with UFH) in smoothed fashion that also reduces the peak stove output to the room. I don't mind felling, chopping, splitting and storing the lumber. As regards what heats it when a potential stove doesn't, I've oscillated between ASHP and just a simple electric heating element. Thanks, @dpmiller, I was unaware of the FHT stove. Sorry, I'm too daft to know what is meant by direct charge, if asked I'd of said that *was* a coil - but obviously not. Digressing a but, I did look at an Valiant AroTHERM plus .

Can anyone recommend a low room output radiant rather than convective wood burning stove for a low energy airtight build ? Preferably with the capability of heating a thermal store and also DIBt certification ? I've already got some Woodfire models on my list and would also have Tonwerk on it were it not for their astronomical price tag. Thanks.

So have I understood correctly in that an enthalpy exchanger operating at 50% moisture recovery would take out 5gm.m-3 of water from extract air at, say, 10gm.m-3 and put that back into the supply ?

Thanks for measurements, I guess what I don't know is what the RH would be during cold snaps without an enthalpy exchanger. @ProDave my concern was that I'll be reliant on the inside VCL more than if the airtight layer wasn't on the outside which to my mind sounded like a potential cause of increased moisture if the internal AH was higher than it would be for four months of the year than without the exchanger.

I am looking at getting an MVHR system with an enthalpy exchanger as I have chronic (non-allergic) rhinitus that seems to be triggered by central heating drying out cold winter air. The build type is to be timber frame and blown woodfibre with Wraptite on the outside. Regarding the wall type and moisture management within it, should I be concerned that in winter the humidity will be higher than it would otherwise have been without the enthalpy exchanger ?

So does a split unit like the Toshiba Mirai mentioned in this thread need planning permission ?

Well, several months elapsed after the planning work no invoice was forthcoming, I had to ask them to send their bill which I paid the same day as it was received - so I'd hope they wouldn't have be down as a slow payer !

They also drew up and submitted the planning, that time charging in arrears.

Architect has asked for payment in full for work on compilation of Scottish building warrant (equivalent of English building regs) before starting work it. Am I right to consider this dubiously ?

Which, if any, of the Scottish regulations set out what site security measures should be in place for the duration of a build ? I have a pre-existing 1m high perimeter fence and am considering bolstering it to 1.8m but want to check what is actually required for building warrant etc Maybe I'm too impatient with google searches but I could not find anything specific.

Thanks to all who responded. I couldn't see how the extra two hours would cause an issue - but didn't want to mistakenly assume that as a given.

I know that the sweet spot is 12 hours, but is having a delay of 14 hours any less desirable than 12 ? Thanks

Has any one else used I joists for the top header plate in a I joist build ? If possible I would like to forward my engineer some example drawings as I want to steer away from solid glulams.

I had thought OSB was commonly used for this but is that true ? I have seen ply also mentioned - so what determines which should be used ?

I guess that might be a problem @ProDave - especially condensate on the floor ! Ah interesting, now I think of it I remember seeing an LG ASHP diagram with showing a fan coil for cooling, I think I tried to find out more from LG and also ask them about an installer and got, well, not very far ! So have I understood correctly in that that solution would cool the air rather the what is connected to the heating flow output ? Do any other ASHPs pair up easily with fan coils ?

Thanks @joth and @Dan F . I guess if clipping the resistor over a couple of pins on the PCB is sufficient alone to get the cooling working without any other measures on the UK units that is a result. Straying off topic ever so slightly, that would mean the installer would be unaware the system would be used for cooling post-install so are there any subtleties that the wider system i.e. UFH, pipework, manifolds etc need to be designed in mind with if the whole system is to be able to run in cooling mode also ? Instincts tell me not as it is the same thermodynamics just with the energy flowing in the opposite sense to warming mode. Interest in these for me was piqued a few weeks back as supplier local to my build (who was previously going to supply and install a Woodfire CX12 and 500L thermal store) phoned me up saying there were expanding into heat pumps and were now a new Vaillant agent - obviously he started extolling the virtues of the new aroTHERM units. I was slightly concerned about the potential to add to summer overheating problems with a thermal store under the previous plan and also to have both heating and cooling delivered by the one single appliance is a potential bonus.

So there is a cursory mention of cooling in the Valliant aroTHERM docs I've so far seen but the supplier I'm in contact with not yet answered question as to whether they will install and commission a new system with the cooling function enabled. Has anyone got any light to shed on using the cooling function on these ? I remember being advised a while back that installing a system that has cooling accessible from the user controls means the RHI eligibility is problematic. Just before the lockdown I talked to someone who suggested this was no longer the problem it once was - is that correct ?

It is JJI joist (350mm wall, 450m roof) construction with blown woodfibre insulation - that too is included in quote.

@Temp Thanks for those, I have contacted some brokers, so far to no avail, but the two more you have listed there might differ in response - though no doubt the uncertainty of risk factor for them might make it fairly costly even if, as you say, they will deal in c2b rather than b2b. @PeterW Sorry - yes windows, veluxes and rainwater goods also included.The internal joinery includes both supply and fit and comprises stairs, first floor, partitions, sound insulation, all plaster boarding, internal doors and frames skirtings, architraves, windowsills etc. They are also prepared to work around the electrician, plumber and MVHR installer that I appoint. External perimeter decking and screening also included. The odd thing is I suggested some sort of title of goods arrangement last week and at first this was met with the claim that it was hard to do as under Scots law as property could only be heritable rather than "moveable". But after I hesitated this week due the risk factor this objection seems to have been put aside.

@PeterW But tidy for whom ?! Remainder of terms are another 25% within seven days of invoicing after principal kit delivery, 15% payment on making wind and watertight and balance within thirty days of completion. The contract isn't only for wind and water tight structure but also includes the roofing, cladding and internal joinery. No retention in their quote come contract.