MikeGrahamT21

Can't find anything online about Tyvek, but Kingspan Nilvent breather membrane claim "Airtight at normal building pressures", whatever that means? EDIT, found it: Air Permeability Kingspan nilvent ® is airtight, when tested at normal building pressures, i.e. 50 Pa pressure difference. Pretty sure the Tyvek stuff will be the same, but i will check, and if its not airtight, i'll consider the Kingspan Nilvent stuff as a replacement for it, it will come in at some point for the roof.

breather membrane is tyvek supro by the way, not the cheap stuff.

Yeah thats the one, sleeper wall in the middle. Are breather membranes not airtight within 50pa? I know they aren't fully airtight. I seem to remember asking someone before, and for suspended wood it had to be vapour open membrane, so that excess moisture didn't collect under the floor and rot the joists, is that not right? We have plenty of air bricks, and good flow underneath, so I guess it shouldn't be an issue, but was just erring on the side of caution. Plus i've got 2 rolls of the stuff! lol

You are correct in terms of air leakage, not much point as it would be below the barrier, but my thinking was to stop any moisture migrating to the joist ends which would be a lot colder. Thought about insulation type, I know fitting PIR is a pain, but with only 100mm to utilise, its the best type per £ i'm going to get. Also, if I use a wool based product, ideally i'd need the membrane below to stop air movement into the insulation, which isn't going to happen. I could lap the membrane over and under which would get the effect i'd need, but that would also be a pain to detail.

Hi, Just wanting to run my plans past someone to ensure I'm on the right track... We have suspended wood floor (using 4x2), with about 200mm void underneath the timbers and my plans are as follows: Clean out all of the rubbish from under the floor and hoover all the dust up Replace any bad timbers (we have had woodworm previously), and treat any remaining good timbers Re-do heating pipes and ensure fully insulated Apply a sand/cement parge around the joist ends, and then seal using airtight tape 100mm PIR friction fit in between the joists to fully fill them, and use expanding foam to fill in any gaps overlay the joists with breathable roofing type membrane, with the 'outside' side facing into the room, overlap by 100mm, and seal with airtight tape. Lap the membrane up the walls slightly, and bond to the wall (possibly using an airtight silicone??) Flooring to be 18mm OSB3 smart ply Skirting board to finish, and cover up the membrane lap Is there any part of this which can be improved at all? Thanks for your input. Regards Mike

No problems, i'll go with the option of installing it in the back gable should we proceed, which will vent onto our own land

Actually, I think a quick google has just revealed the answer to this one, its a no go! We can put it on the gable end either end, so I'll have a ponder about it and see what I can come up with.

Hi, I'm thinking of installing a Single Room MVHR to our new utility, which will protrude the garage wall by around 50-70mm if I remember right, and we have the option of either exhausting directly onto the neighbours garage (between the buildings there is around 700-800mm), or we can exhaust over his driveway. Now he has been very funny over the years, so I thought this was a sensible question before i crack out the old core drill. Are there any legal issues or come back potential here? Mike

I've seen these type underfloor heating systems before on the internet, and was very interested in them, makes sense I guess using larger area to heat, just seemed a bit too good to be true.

OK, was worth considering, but yeah I do worry about the cool air intake, even from the heated models, only gets to 10c, which seems a bit inefficient. PIV is a lot cheaper to buy, but i'd prefer to buy MVHR and have all the benefits which come with it. Installation will be done by me, following someones design, so costs from labour point of view are nil.

Also, what are your views on Positive Input Ventilation, and d-MEV as a whole system, and I'll monitor the loft for smells. This obviously wouldn't capture any heat, but would still fulfil the air quality side of things.

Yeah i think thats got to be the next step. I'd say a good 80% of the time it must be westerly, however we did smell it quite often last year in the front (nearest to them), so this may not necessarily be the case.

Neighbour is east of us, so normally with west wind, wouldn't be an issue, just those odd times when we get the cold easterly's. I'll keep an eye on where it smells, the back of the house is always better than the front, but i'll take more notice this winter.

Thought that might be the case too. Ah well, at least I'm going into this with my eyes open, last thing I want is to install all this and be disappointed. On the plus side it gives me a free £1500 to go toward battery storage for our PV when it becomes viable (going to give it some time to develop, as things are hotting up), you never know may even be government incentives in the coming years.

Yeah thought it might :-( Oh well, I guess i'll keep an eye and a nose on where the smoke actually gets to around the property, and hopefully there will be somewhere which is smoke free. Would MVHR actually be worth the cost and effort, if we couldn't use it from say Nov - March?

Another question on MVHR units... Is there any way to operate them in Extract Only? I'm just thinking so we still have a ventilation method to remove excess moisture during times of smoke when we don't want to import air? I guess the air would just come from other places though wouldn't it? And probably be no better off?

Thanks, i've added that to my watch list.

mmm, I think i'd agree with you there! Perhaps BPC are just on the sell sell sell tactics. Plus the filter they recommended is a whopping £800 for the smallest one! And no guarantee of if it doesn't work can i have my money back. I'm going to pay more attention to where we can smell the smoke this winter, it may be that we can only get it at the nearest point to the neighbours house, though i guess it probably depends on the wind direction! They are to our east, so more often than not the westerly's carry it away, but get a cold easterly, and it would definitely be on, and coming in our direction, so its not looking promising! I'm really annoyed to be honest, as I've been dreaming all this up for years. We do seem to suffer from quite high humidity in the house (if i leave the dehumidifier off we reach around 70% in occupancy, dropping back to 65% if we go out), which this would have cured, and currently resolve this using a smart dehumidifier, but obviously it takes a lot of electric, though does give us some heat back being a dessicant version, and this brings it back to a more reasonable 60%, though we can go to 50% if required. We have an extractor in the bathroom which is PIR activated, so is on regularly, but perhaps isn't powerful enough. I don't even know whether to consider a single room MVHR for bathroom when this one breaks, as we'll be in the same situation, just on a smaller single room scale!

I contacted BPC for a free quote, they didn't seem too concerned about the smoke issue, said that the units all come with filters which should get rid of it, and if its too bad, they sell an £800 carbon filter as an extra which would see it off. Opinions on this? I know someone recommended BPC, but they seem to be saying the exact opposite of you guys, and its a lot of money to spend!

Thanks! As soon as I saw the car radiator fan I thought it would be ideal, and very cheap too! Do you have a link to a speed controller? I'll have to give this build a go at some point, should help me massively moving forwards. Got some plywood coming up for use, its temporary flooring at the moment, so this will be a good use of it :-)

Back to my home made blower... I've found the specs of another blower door online, which states: Maximum flow @ 50 Pa 5450 cfm (9265 m3/h) Highest flow of any portable blower door Our house is only small, so I'm not going to need anywhere near that surely? I've had a thought about using 1 (or maybe 2 to get near this value) car radiator fans? http://www.ebay.co.uk/itm/16-120w-Aeroline-High-Power-Electric-Car-Engine-Radiator-Cooling-Fan-/172428823084?epid=0&hash=item28258f0a2c:g:YKQAAOSwkNZUq~Yv This one will push 2500CFM for £30... What do you think? Linked up to some kind of potentiometer to vary the speed?

With a level of 0.6ACH, is the slamming only possible because you have the MVHR vents in place? As this would balance the pressure difference between the rooms, which I presume is what makes the action slightly harder, i.e. it has to balance via the door opening whilst its getting smaller.

Yeah I was referring to the external doors, sorry! The internal doors are also a tiny bit harder to close, these have a 10mm gap underneath, and when you open them with force with no windows open, you often hear the ceiling making a few clicks, with the air rushing in through any small gaps (and i know there are some!)

Yeah, the closing door thing is obviously not a very good way of testing, but without machinery I thought it wasn't too bad to see how i'm getting on, coincidentally, the doors are definitely harder to shut the more work i do, as said with the utility you physically cannot slam the door closed, no matter how hard you try. I had a think last night, how much air would a load of 100mm delta fans (computer fans) fixed onto plywood push? I remember they are quite powerful (and noisy!). How much air does a blower fan push? (I'm guessing quite a bit). I certainly would like to depressurise the house to get a better understanding of where all the leaks are, some are obvious i.e. the big hole in the kitchen floor under the oven, but I know there will be a lot of smaller less obvious ones. Since the idea of MVHR is now just a fading memory courtesy of our neighbour, i won't be going to extremes in order to avoid poor air quality, but i will still be laying taped membranes under the floors in order to do the best that I can, which has always been the goal, taking the principles of what is done to achieve passive house standards, and applying them as best as I can to our house without spending silly amounts of money, I think this will go a good way to reducing our energy demands, and indeed year on year we are requiring less gas for example (I know its hard to directly compare one year to another as they are so different).

OK, and I'd be right in thinking that 3-5ACH is going to be quite hard to achieve? How hard would it be to close a door at those levels as an example?