phatboy

Sorry for the terribly slow reply.... family life happened and nothing else got done! Since starting this thread we no longer have pets in the house, and so the bedroom door now remains open when we are home (Someone is here most days). This seems to have cured the issues during the recent cold spell, so the issue seems to have been that the room just inadequately heated - it has a 800w panel heater that's always on and is set to keep the room at about 18 degrees. Last year, before the MHRV was fitted, we did run a dehumidifier for 2 hours each morning and that kept things mostly under control, except for the corners. Thanks for all the replies, much appreciated. Tim

That's what I did on mine too... inserted a connector to the solid pipe and taped, then attached the flexi with a worm drive clip, then taped over that too. I used the fabric flexi's though, and there was no way at all they were going to go over the pipes any other way.

I only had a silencer on the supply, but fairly quickly added one to the extract as well. The rooms with extract you can tolerate more noise, but it was still noticeable. £25 later and the entire system is almost silent even on boost.

That's a lotta reading!! I will have a look properly tomorrow. I'd like to think my system is well installed - I took a lot of time over it, as it was to be for my own benefit / enjoyment. As you have probably seen elsewhere I had considerable issues with the balancing but I think that's resolved now, I'll be re-measuring everything this week sometime to confirm.

Worth a shot I suppose! I'll soon be told if it's a problem. No actual VCL correct. I never did an air tightness test before commencing, intended to run the supply side of the system higher in order to compensate for any leaks. I've made damned sure the windows and doors are well fitted though. I knew I was never going to get to a passive house level with this place, to be honest at the beginning I didn't even know about it, I just knew black mould up to chest height on all of the north and east side was not on!

Wow it seems I've kicked off quite the debate here! I appreciate all the advice, so I'll reply! I really appreciate all the replies, and it seems my 'simple issue' may be far from it! Yes solid walls, no void. 9" standard blocks laid on their side. Hard plastered, existing cement parge coat, existing skim, then a re-skim re-done when we moved in. Yes HMRV was fitted as after all the insulation works were done, some corners and behind the bed still got a bit of mould, but nothing like when the house was uninsulated. The damp course could be seen until the EWI went up. Air bricks vary as we are on a sloped plot. Closest is about 2" above ground level, the ground is a paved driveway. We are also on sand. Air bricks are DEFINITELY below the DPC. I hope not, as it's all now in! The issue I guess with lots of ventilation is the draughts. I won't question any more on what you said until I've had a chance to read fully the other thread JSHarris has linked. I was pretty sure the issues we were experiencing were due to air not moving enough, and MHRV seemed a better choice than PIV. Technically yes, but it would pain me hugely, and the wardrobes would need to go against the north wall, probably making things worse! Re-assuring to know you fixed the same type of issue in the way I proposed. I could, however I don't want to over-ventilate and get a cold shoulder at night. It may be something to trial! Usually in the tumble dryer, which has an extract vent almost directly above. Sometimes it's done around the house, but the experience of others seems to be that with HMRV that's OK?! Yes just the 1 bathroom, we dream of an en-suite! There are 3 extract points: Bathroom, kitchen and utility room. It would be tough to add another now... the loft has been insulated and floored over. The mould does form very close to the supply valve though, near floor level. Yes there were, that's pretty much why I installed the system. The moisture was always worse in this room, but all rooms experienced mould in the top corner where 2 outside walls met. And behind furniture close to the wall, even with it all spaced off 2" with timbers. As suggested by @ProDave, I do already have an IR thermometer, used for sick children. It does have a surface monitor setting which I used extensively last year Right now, the north wall in that room is showing 1.5degree Celsius cooler than all other walls (roughly). I'll gather more stats tomorrow evening, even better if it's a cooler day. Thanks again all. Tim

Sorry I've not made things very clear! With the MHRV I cannot have an extra extracts (presumably), nor should I need to I don't think? Please see attached room with issue, and whole house MHrV design. The problem room is Bedroom 1. Thanks again... Tim

It's in the furthest corner from the door (about 4.6m), in the north - east corner About 10mm. Boost flow rate for that room is 6l/s Thanks Tim

Thanks guys, The house is a 1950's bungalow, 9" solid block walls. I have insulated under the suspended floors with 50mm Celotex (I know it should have been a bit more), loft topped up to 300mm, 90mm EPS EWI. I used extra loft insulation to go right over the block work, so the house should be in a 'tea cosy' really. So we are pretty well insulated now. It is the bedroom, a room that has its door closed and so is cooler. I suspect it's moisture from the shower... previous years we have run a dehumidifier for 2 hours a day to stop it, but this year I've not started yet and hoped the MHRV would resolve things. Based on seeing the EWI being installed, I am quite confident there are no cold spots on the walls, and I did the floors and loft myself. I assumed it was just that some moisture would always be around, and it would find the coldest surface (north) and there always would be a coolest surface. The lack of air movement behind the bed caused it to settle and not get moved on. But if you think otherwise, I'm all ears....! Tim

Long story short, we still get mould behind the bed with MHRV running. It's held 5" away from the wall with wooden blocks, but with the bedside units air circulation is still limited. And the headboard is tall. And it's the north wall. My current thinking is 1 or 2 12v silent computer fans running all the time, or maybe a on a timerswitch on some programme. Is this the best way, or am I missing an obvious trick? Thanks! Tim

Thanks @JSHarris, that's the re-assurance I needed! My extract runs are all very short, so I'm still a little surprised, but I'll put it to the back of my mind

Finally got the parts, and a bit more time on this today. I've pretty much got it balanced - it's definitely a good work out, and a little frustrating as every adjustment changes all remaining valves. I'm just a little unsure as to why it's balanced with the supply at 50%, and the extract at 70%?! This seems like a massive difference, and I'm not aware of any leaks. Does anyone have any thoughts as to why this may be? I wonder if having 2 of 3 extract plenums with 2 connections has some sort of influence? Would like to get this project marked as complete now! Thanks Tim

Concave are the supply, and those like you have are the extract, in my BPC supplied system. I have standard height ceilings, and since the vents were installed in March / April, I've never really noticed them when entering a room, or really whilst sitting around. Bet I will now though.....!

Outside is definitely the proper way for heat reduction film. You wouldn't want cracked glass! Too sunny is also quite feasible, we did ours early morning whilst it was still in shade as there was a risk of the water used to keep the film movable and push bubbles out could dry before we had finished getting the film right.

In the end, I went for Solyx UltraCool-IR70 Solar Control Film. It's certainly helped since being installed at the end of July, the temperature in the south facing bedrooms has reduced by 2 degrees Celsius, matching the temperature of the east facing rooms. And that's without the blinds even being down. It does also claim to help keep heat in during winter, but only time will tell... Fortunately I have a friend who is experienced in fitting the films, and has access to a cutting machine, so 6 metres of film was £250, cutting and fitting was £50

I was advised to fit extracts near to the centre of the room, and supply close to the farthest corner to the internal door. I hope it's right, as it's done now ?

Things are looking a bit more positive now! I can get the system roughly balanced, with the system at 60% boost extract, and at 90% of BPC's recommended flow rates. I've asked BPC to supply me with a proper restrictor for the utility plenum, as this is the one I was struggling to get to a low enough rate, to get the others to a high enough rate. Tim

I've found the spray gets a good neat finish. Always painted where visible so not noticed the yellow before. Know of anything as good, but that stays nice and white?

Sticks Like certainly seems more 'runny' than CT1 in my experience....

Still not had much luck with this.... I don't feel the unit should need to run at 80% on boost for a house the size of mine. BPC looked at the rates they provided, and said they were wrong and re-did them, requiring a slightly higher overall rate! They also said I needed to set the Cooker Hood ''Normal' and 'Boost@ settings to 100%, even without a hood fitted - maybe a useful note for others with a Vent Axia unit. Hopefully at the weekend, I will try and balance it up at 90%, or 80% of BR requirements and see how I go. Reality seems to be nobody wants to run their systems at BR rates anyway! Tim

I assume everyone has gone outside to enjoy the weather, but hopeful that one of the resident experts will be about again soon. I'll try BPC again tomorrow, but whenever I've called the person who deals with these things isn't there ?

Get into Cable mode (mines older so it's called VWRAP, and you'll be sorted Yup if you drop it it will survive, less so your toes!

Hi all, I've been trying to balance the system today, and am struggling. House is approx. 95m2, on 1 level only. 5 supply, 3 extract valves. MHRV unit is a Vent Axia Sentinel Kinetic BH. Supply (1 75mm pipe to each plenum) I can get this to balance at 60% boost easily. Extract (2x 75mm supply pipes to kitchen and bathroom, 1 to Utility. Pipe runs are all very short, no more than 4m) Won't balance. When I get the system to 65% boost I can get the total required airflow, but I cannot reduce the bathroom and utility plenums to their required values, and cannot increase the kitchen to it's required value. At 100%, there is plenty of flow everywhere. Do you think I need some sort of restrictor inside the plenum to reduce the output? I am using these plenums: https://www.bpcventilation.com/90-plenum-round-pipe-airflex Also, for a house of this size, should I need boost levels so high? The unit is spec'd to be good for up to 150m2 of floor area. Feeling a little deflated, as all if the installation wen't very well generally. I have also ensured there are no air leaks and foil taped up every join on the 5" side. Any tips or guidance much appreciated as ever. Tim

Yes they are. That's a little concerning, how did you resolve that?!

Sorry for filing the forum with my topics tonight, I've just reached the point where I finally turned on the system tonight I will be submitting a full detailed end-to-end project post with photo's sometime soon, to save people re-asking what I've been boring you with. So, I grossly over-ordered from BPC, as I knew I couldn't easily return anything because I'm in Jersey. I have 10 linear metres of 5" pipe to insulate with their 25mm foil-covered itchy glass fibre, and a total of about 5m of pipe to wrap. Is it worth doubling, or even tripling the insulation around the pipes? The outside temperature never gets below zero here, outside gets up to about 33 occasionally. I remember someone, maybe @joe90 doubling up, but cannot find that post and reasons why now. Thanks Tim