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I've had this by email but it doesn't mean much to me. Ignore if it's old 'news'. Or let me know if you want me to find the whole article. BS 7671 adds battery guidance 2 hours The BSI and IET have updated the Wiring Regulations, BS 7671, with a new chapter on battery storage. Domestic solar is often supported by battery storage. The new chapter covers stationary secondary batteries, responding to the rapid growth of energy‑storage technologies and their increasing deployment both with and without solar PV systems. It sets out requirements relating to system

I was thinking the same Nick re the use of AB before boarding, am assuming also better to do 1st fix before to allow the AB to seal everything up? Think we will also have to use something like parge or poss some membrane behind our pole plates as they will obv go in before and not sure the AB will penetrate behind those once they're in. We were graduating towards float and set plaster as think it would go well with the woodcrete but, a. I'm not sure we will easily find a plasterer who's skilled in that, as d&d has been the preferred for so long now, and b. feels a bit like overkill using that and the AB. Still so many choices to make.....

Most heat pumps only heat the house OR the hot water, never both at the same time. So if you use 24kWh of hot water in a day and want the HP to heat it, the heat pump will spend just over 3 hours heating the HW leaving only 21 hours available to heat the house. So your 7kW HP will over those 21 hours add 147kWh to the house. That's an average of 6.125 kW over the whole day. Not sure where you are but designing for -2.7C is not very cold. Here I designed for -10, a very real winter temperature.

That is the answer to the ventilation anomaly. The reduced method by CIBSE only accounts for naturally ventilated (with extract fans etc.) or continuous MVHR, not for unbalanced whole house situations such as PIV or MEV. In these cases the full BS EN 12831:2017 method needs to be applied - hence coming soon to the tool. There are a couple of notes in the app, but I don't think this is clear enough at the beginning where the initial Ventilation and Air Permeability settings are input - so I will make sure it's clearer and explained properly for users. There's also a drop down at the bottom of the room editor to select continuous mechanical ventilation and if unbalanced is selected there is a note to say it is outside the current method scope. Again, something natural for me as the designer, I therefore easily overlook it as not that sensible for a user! Thanks.

@SimonD This is just what I am looking for, we are embarking a [very] long term project on our village hall, 1) Solar / Battery, 2) Insulation/ventilation 3) heat pump. And each stage will depend on Grants/Funding. It's our view that 3 will only become feasible with the other two in place as currently we do not heat 24hrs/per day so have, but we need an end point I will get some measurements plug them in and get back to you.

Don’t need a 4th. A separate lounge area would be nice I agree. I can then put a sofa bed in there if a 4th bed is ever needed

Yes exactly, if I do marble on both sides then might need denser blocks. The combination will add so much load we might need to revise and thicken the steel frame for the building. All I was trying to ask was which lightweight block product can take the most load.

Seems a bit bedroom heavy to me! Do you need a 4th bedroom? More than 50% of the space is bedrooms/bathrooms, which are much less used than lounge kitchen areas. I would maybe think about a separate TV room so that the lounge can be a more relaxing area.

Totally. For woodcrete I’d get them in before you have boarded, as that will allow you maximum exposure for the magic goop to do its thing. Follow on trades will all need inductions and in agreement to maintain the integrity of that airtight layer. On an Isotex job the client tried a liquid membrane, spray and brush applied, but the woodcrete simply has too open a pore for this to work well on bare woodcrete. Another parged first and got 0.66ACH, but neither were ‘cost effective’ (they were expensive as feck). AB is your friend here, but obvs a certain amount of prep needs doing ahead of their arrival.

Cryptic.. good luck

You deserve it too. You've written three pages, and I've not understood a word.

Front where the garage is

I think OP said he was restricted to 350mm total due to foundation. My point is by the time you spend upwards of 2k on 25mm pir, 25mm battens and lose 50mm of internal space it doesn't seem economical

@Nickfromwales posted a shot of this replacement mixing valve in "Drop in Flow Rate" (2022) but didn't say if it cured the problem, it seems a very simple device and one might think that if the valve is moving up/down with the pin that the valve should be wide open to the hot flow with the actuator removed.

Our calculated heat loss is 8.5kw at -2. We put in a 7kw LG Therma V and it's kept us warm all through this winter but it's worked very hard for the few days it's been freezing. I was wary of oversizing for the reasons JohnMo mentions and was wanting to install an 8.5kw Ecodan to exactly match our heat loss. The LG came up on ebay secondhand for a few hundred £ so went for that with a plan to run a fan heater or light the woodburner if the smaller LG unit couldn't cope. No fan heater or woodburner needed as the smaller LG has coped throughout and I'm very pleased with how things have worked out. We'll hopefully have benefitted from efficiency gains in running a smaller unit but the older Therma V doesn't calculate COP or energy produced so I'll never know for sure.

Reviews are really good for it . Most people just email / web browse e.g waste time on here - it seems very capable for that . I only about 6 months ago bought an air and tbh Neo would have been fine as compiling/llm/heavy work always done on server type hardware ; currently the m3 ultra . But you know what ; I’m having a break 😎

First heat pump name plate ratings are meaningless. They all take a different datum point for the rating. Vaillant tend to use a low ambient. Worst thing you can do for efficiency is oversize you heat oump. On the design day and they don't happen often you can always flick on the immersion, but doubt you will need too.

Wider cavity. It's not rocket science. We have 250mm.

Where's North?

OK that makes sense - I considered removing all the doors from the landing the whole landing, hallway stairwell area is also a bit tricky I broke it into chunks to make it easy for me as they are all linked but only one radiator (albeit a big one) is in the lower hallway (so the tool says it's oversized) however if I add all the reqts together it's in line with the other rooms It used to be a 550 by 800 T11 - it's now a 500 x 1400 T22 Makes perfect sense - before I insulated between the joists of the ground floor with 75mm PIR you could feel a draft in most rooms when the wind got up - now it can be a bloody good gale outside and there is no drafts at all........ I know I've got the house reasonably well sealed hence the installation of a PIV unit to manage humidity and ACH's (But it's not MVHR )

If those are known quantities, then yes, change the dT. The standards just ask for default values, so an MCS design requires the use of the default Design Outdoor Temp as the difference with suspended floors. There are some aspects where deviation is okay for MCS designs but you have to be prepared to justify them if asked.

That's actually what I do when I have a space like a hall or landing and when I have rooms with large open plan openings, so I create a non-existent door - as long your room dTs match, and set to 0 then it doesn't impact the fabric losses. It also shouldn't affect the ventilation losses because the exposed envelope is set and the calculation uses that. It's a bit prescriptive on the ventilation, so there isn't anything immediately available to make adjustments to this ventilation factor. There are still some questions about how BS EN 12831:2017 treat ventilation and the CIBSE guide uses a bit of SAP in there. I'm going to have a think about this one. It's really the way it's calculating infiltration leakage which is giving you the high figure, but you've got to be a bit careful how you interpret the Ventilation - Emitter Sizing. This calculation isn't saying that you are going to use this amount of energy at a given time, which is your Fabric loss and Ventilation - Generator Sizing. The Ventilation - Emitter sizing, although provided as a total, should really be looked at in relation to individual rooms because it's essentially calculating the effect of high winds on each room based on the exposed area. So at any given time the rooms won't be losing all heat to the outside, but transferring to other rooms within the building. But high infiltration will increase the heat load within the room subject to high infiltration and so the standards are encouraging us to install slightly larger radiators and thus improve efficiency. Does this make sense?

So we had the £250 Heat Geek survey. They have come back with a proposal for a 7kw Vaillant heat pump (apparently they only do Vaillant under this offer) Their heat loss calc says that at the reference temp (-2.7 here) the heat loss is 7.83kw. I know this is about accurate and our rads support this at a flow temp of about 45C WE heat our hot water by immersion and use of order 24kwh per day. There is no proposal to change the tank so lets assume that at the -2.7C day the cop on hot water is only 2. That means another 0.5kw of heat energy needed on average taking it to 8.23kw. And that is before there is any thought about recovering an overnight setback or other unexpected heat loss (power cut, windows open for painting or whatever). Too me the 7kw sounds under powered, are there any charts for its output at different air and flow temps to suggest that it would be powerful enough? What would people think would be the correct size heat pump for this heat requirement - I think we need a unit that provides 9 or 10kw at -2.7 air / 45 flow. Thanks

Last point - pretty sure it's ventilation losses that are driving the higher calculated heat loss Fabric is now 4144 W Ventilation is 3090 W Anyway to reduce that ventilation factor? I guess I see a blower test in my future

OK checked out the changes - made a couple of tweaks now I understand the logic More stupid questions 6 rooms upstairs all have doors then I treated the landing as a room and put 6 doors in there.......... Ceiling for all upstairs rooms is plasterboard & then 300mm Insulation and over boarded - temp in the loft is always 2 to 3 deg above OAT should I be lowering the delta from room to ceiling Same with the temp below the suspended ground floor it's always higher than OAT