Triassic

Looking through a couple of the quotes, both suggest using a pair of 63mm ducts where the single duct airflow is too high. I assume this is the approach others on here us? In my case Smaller diameter ducts would be easier to run. Could I terminate these in separate outlets (in the same room) rather than one single outlet?

I'm currently calculating the duct size for my MVHR system. What air flow is the 'ideal', what is too high? Some of mine are at a maximum of 3.7l/s in 63mm duct, or 2.3 l/s in 80mm duct. Not sure who produced the attached MVHR sizing spreadsheet (I stumbled across it whilst reading up on MVHR sizing), anyhow here are the results. Any observations? MVHR_Sizing.ods

When the cooker hood is switched on the boost setting kicks in on the MVHR unit.

Have you published your data sheet on here? I don’t recall seeing one that included Vthrough?

@tonyshouse I'm spending today trying to get to the bottom of the design I actually need. Just as you posted I came across these design and testing guides, which Ive linked to below for anyone else looking for help. I'll take on board your duct sizing suggestion, we live in a quiet rural location and really don't want to be lying in bed listening to some wheezing MVHR system, Id rather listen to the birds! Mind you the triple glazing has put paid to that!

Although the house has four floors the top one is a single room, a study, located in the roof space. We only added it due to the spectacular 270 degree views of the valley below.. But why, my house is no larger than others are building on here, all of whom have a single unit. I’m wondering if the MVHR supplier is doing a designed to some sort of worst case scenario, rather than passive house? Clearly I need to do more work as I really don’t need to spend an additional £3,000 on another unit that will according to most here be turned down to the lowest setting once commissioned.

I’d recommend you get a Utility Shed, I knocked one up out of weather board. We keep the washer, dryer, our work wear, boots, veg and little used stuff in there. I also use it as a changing room, so I’m not trudging dirt into our living space at the end of each day.

@HerbJ thanks for the link, Sorry it’s taken me a while to get back on topic, I’ve been fixing cladding between rain clouds and airtightness membrane otherwise, Clearly I need to do some reading and more work to get to a more sensible answer. I emailed the two suppliers who quoted and asked for the rational for specifying two MVHR units, in both cases they said it was because it was a large house and needed two units! My house is around 380ms, including a large entrance hall, stairs and landings (60m2) over four floors. On first glance at your approach, am I correct in assuming you really only need to extract from those rooms listed in Part F and put fresh air into accommodation spaces such as bedrooms and lounges and things like stairwell can be discounted?

They are! I was quoted £1.98/m2.

We’re having a brick feature wall in the stairwell, into which we’ll fit a steel staircase. The supplier is offering either 65 or 85 mm thick bricks. Has anyone got any thoughts on which to go for?

Is it cost effective? Others on here have questioned the payback time, particularly when you consider just how cheap electricity is if taken during the night? Why not use a Willis heater and save the thousands it will cost to install a gro7nd or air source heat pump?

I think this is part of the problem, it took them three attempts to get the design right, they suggested siting one of the MVHR units in a loft space that did not exist, then they moved it to a room without outside walls, making it difficult to run the 180mm intake and exhaust ducts, they would not fit through the gaps in the metal web joists.

+1 for Tool Station. Order online with free delivery to site.

Thanks for the response, a quick look through my quotes and none mention RH being a problem in a high volume house.

I'm struggling and need your input. I've rather foolishly designed and build a large volume house. The Kitchen / family room, the master and second bedrooms all have cathedral ceilings, as do two of the en-suites! I send my drawings to a number of MVHR suppliers who offer design services and got three quotes back, each one was different in what was specified and none provided technical detail around calculations. The simplest design was a single MVHR unit and at the other end of the scale, they specified two of the largest units on the market. I'm now thinking I need to do my own calculations and try and clearly identify what is required to meet Part F of Building Regulations. From what I've read in Part F, the Whole house Ventilation Rate is 25 l/s (based on 4 bedrooms), however, the minimum based on floor area is 114.58 l/s. Having done a spreadsheet (below) it would appear that I need more air extraction to meet the minimum ventilation rate? I assume the input air designed to balance the extract rate? Looking at the first of my quotes they suggest a single unit 650m3/h, the other quote suggest two units with a total 985 m3/hour. Am I on the right line here, or am I missing something? All help gratefully received!!!!!!

I always use compression fit valves. Never had a problem so far!

I'm back at the self build (and the internet) with a vengeance, having had a good rest over Christmas. Ive just added up how many of the fancy manifold outlets I would need for my hot and cold water, its 32! Given that they are around £12 per outlet, that's £384 in total. I've decided to go down the @joe90 route and us a 4 way push fit manifold at £7.50 each, giving a price of £60. I realise that these don't include a service valves, these can be had for 80p each, giving a total price of £85.60. A total saving of ££298.40

I'm at the design stage, I used BPC having seen them recommended here. Out of interest where did you source your MVHR unit and kit from? I've also got vaulted ceilings and BPC has said that due to the total volume of the house I need two MVHR units, not something I'd considered during the design (ouch!) so cost have doubled to £5,885 as a result, hence my desire to save money where I can.

Last night I emailed one of the suppliers who asked for feedback, I sent them a link to an online source (they wouldn’t sell to me as I was outside their delivery area) and they have just emailed to matched the online price of £5.72 +vat.

SIG have, after a number of phone calls, just confirmed a price of £6.15 per 2.4 x1.2 sheet 12.5m, thick. This is the cheapest I can find having phoned and emailed a good number of suppliers. To be honest I thought I’d get a better deal given I need over 300 sheets. @nod who do you use?

They just quoted me today £6.42 ex Vat per 2.4x1.2m sheet.

I’m starting plaster boarding very soon and recall someone recommending a good value supplier, could someone remind me who that was? I’m specifically looking for 12mm thick by 2400 x 1200mm. The cheapest I’ve found so far Is £7 as sheet, reducing to £6.65 if you buy over 250 sheets, inc VAT.

In the last renovation we dug out the ground floor and filled in the cellar, we then fitted polystyrene insulation, with concrete above. We self installed underfloor heating, fixed using cable ties, to steel mesh reinforcement. In the upstairs rooms we fitted wall radiators. I’d suggest you use modern insulation rather than sheep’s wool, as it’ll take up less space.

Wasn’t CIL implemented on different dates by different councils. I've checked my records and i also didn’t receive confirmation of receipt of CIL. I have a note in my diary for a phone call to the council, I noted that the person I talked to had no idea what CIL was, I foolishly never followed it up. I have no desire to follow things up at this stage! How do we lobby for simplification of the rules to make it more human?

You can buy airtight OSB, no doubt it’ll be a premium product with a price to match