Savage87

@Oz07thanks! bump, does anyone else have more to add?

I need to fit roof terminals for extract and supply ducts. My roof has 2 sides, one towards north and one towards south. This is a mid terrace house. North side is to the front of the house, facing a busy main road, so it's cooler and more polluted. South side is facing the back garden and gets hotter. I live in the MK postcode. I think winds tend to blow from the west. If this is true, do I have to put the supply pipe towards the west and extract towards the east? I don't know what would be best? Also, I was looking at the different types of semi rigid ducts on BPC's website. I would like to get the best one I can, but I don't want to spend anymore than I have if there is no real added benefit. So, what did you guys have installed? standard, anti static or anti static and anti bacterial / basic, standard or premium?

sounds good, keep us updated! ?

Did you eventualy get a proper test done?

Sorry it's taking so long to reply, I have done some careful considerations and we will be going ahead with the MVHR unit. I'm still considering the Domus HRXE to other unit. The unit should work at 75% performance on boost and this will satisfy BRegs. Once BC has been round I will turn it down to 50% and that will be sufficient based on the calculations that I done. as suggested by @PeterStarck I have calculated the air flow/velocity through the duct and hopefully the system will be near silent at the valves. In regards to the blower door test, I will definitely get one done but I think now isn't the right time for it. I have watched a lot of videos on how to look for possible leaks and how to fix the them. There will be a lot of work involved, but I'm confident that I can do it Just to clarify a question that I had previously. The presssure loss in Pa on the performance graphs of the units is about the pressure in the whole system. Each component in the system(ducts, bends, silencer, etc) depending on air velocity creates resitance. This all ads up and it gives you the total pressure loss, so the more air resistance in your system, the more pressure loss you have and the harder the fans have to work to supply the air flow required. @joth when looking at how noisy units are you can't really make a good assesment based on the sound performance charts alone because they are all different. I think it's better when you take into account other peoples view and personal experience. Ducting system that I'm leaning towards is Airflow Pro 75mm round semirigid. What do you guys think ? @pocster What are your thoughts about your system/unit? @Jeremy Harris I love what you done with the homemade blower. How did you calculate ACH and pressure difference?

@JSHarris I hope I understand what you said in your last post. Do the above figures match with what your were saying?

@JSHarris From the chart that I produced on my first post the values in bold 14.78 + 14.82 l/s = 29.6l/s this is for the continuous background ventilation rate which exceeds 0.3l/s/m2 ( 90 x 0.3 = 27l/s) have I calculated this correctly? The extract rate from designated rooms are shown in l/s below and I can't acheive under normal operation mode, but will be able on boost @NSSI would love to get this done now but the house isn't at it's best at the moment. The kitchin is back to brickwork. I also need to get a window replaced. I will also look into the homemade blower idea.. Thanks! @JSHarris WOW, that's impressive. This is the extent that I'm willing to go to as well. I have replaced all the ceiling, nearly all of them have been plastered, apart from the spare bedroom which is yet to be plastered, and I have coving on them as well, the hatch to the loft is airtight. The electrical outlets might have some leaking but I'm willing to put the work in to make it better. @jack ... More often than the current state of the house, where you have to open the windows for a couple of hours to get fresh air in. For example, I still have radiators upstairs and in the morning we open the windows upstairs for half a day and that's it. Downstairs we don't open the windows that much and the heat stays in for longer. With the MVHR unit I would have colder air coming in more frequently, does this make sense?

Thanks for bringing this up. I haven't had an air tightness test done. I would like to get one done. As is stands, I'm hoping there's not much leakage in the house as everything is insulated, I have double glazing, the 2 chimneys have been sealed of, so I'm hoping this will bring the values down to an acceptable level. If I do the test and the values are high I will try to seal everything of as best I can. I understand that this is really important but I'm also looking to get fresh filtered air in the house without having to open the windows. My wife brought an important question up. If the unit has in theory 90% heat recovery and you change the air in the whole house every couple of hours, wouldn't this mean that you have to use the heating more often? For example, if it's 23 degrees in the house and in 2-3 hours it might go down by 2-3 degrees because of the constant ventilation wouldn't the heating kick in more often just to keep the desired temperature? I didn't know how answer this question and I hope some has a good answer

Thanks for letting me know. What I'm planning to do is insulate the loft below the rafters, alternatively I will insulate all the ducts in the cold areas to avoid condensation.

To balance the system out, I can only meet BRegs on boost and I understand that this is acceptable.

I've seen these charts on a lot of units but I do not fully understand them. I do understand that the lower the number in dB the quitter it is. I don't know that the different frequencies are all about.. Looking at the Domus HRXE Breakout sound performance chart it says that it really quiet on speeds 1 and 2. I'm planning to run it on speed 2 for normal operation mode.

Thanks @everyone for your quick replies! I'm impressed. I appreciate all your help and I understand that your advice comes with no liability! Any input is good input, I won't just rely on the answers I get on this topic, I will do further research as well and I will take full responsability for this project! @PeterW I had a quick look at the Boulder units and I think the Domus unit is better (I hope I am right ). Also you mentioned about hitting building regs. Do I have a choice? I am under the impression that I need to hit the minimum targets. The main reason I want to put the MVHR unit is because of air quality, I don't have any damp/condensation problems. All the house is insulated, floors, walls and loft and I live on a main busy road and each time I open the windows I'm thinking that a lot of pollution is coming in as well. @Nickfromwales I have already done my own underfloor heating for the whole of the ground floor. It's been running for a couple of years and I have no problems with it Like I said above, I will take full responsability if anything goes wrong @jfb I was thinking that I need 2 ducts going to the kitchen, I was kind of hoping that I needed 1. @JSHarris I will fit some silencers on the supply, the extract I don't think I'm too worried about. It's the bedrooms and the living room that will need to be silent. The last think I want is the wife constantly saying that she can hear noise from the air vents. I kind of have to fit the unit in the loft, as I tried conving my wife to put on the landing and building a cupboard for it but she doesn't want it. My loft is unheated but I have more than 300mm of loft insulation and all of it is overboarded with chipboard on a railing system https://www.amazon.co.uk/LoftZone-8x8USAVE-StoreFloor-Loft-Decking/dp/B00SX0VNT6 . I'm hoping this will keep the noise in the loft. The duct runs won't be that long as this isn't a big house. I'm hoping that I can keep the unit on low so it produces the minimum amount of noise. @vivienz the unit will be above our bedroom but like I said earlier, I'm hoping that the loft insulation and boarding will do a good job. @joth I had a quote recommending the Zender ComfoAir 200. Which is a good unit but a bit pricey and I do understand that I need to spend more to get a better unit. I'm hoping to spend less than 1000 pounds on it. @Ed Davies I got this chart from another topic and used it for my house. The chart was done this way just so I can balance the supply and extract. The extract side isn't enough to satisfy building regs (minimum extract flow rates from the kitchen (13l/s), bathrooms (8l/s), utility room (8l/s) and WC (6l/s)) in normal operation mode, so I will need to set the boost to meet the minimum flow. If something is wrong please let me know. The system shouldn't be used in boost mode in the night time, as you said, it will be a lot louder.

Hello everyone, I'm Alex, I moved in to my victorian mid terrace 7 years ago and I have been gradually been refurbishing it over the years and now I'm at the last stage doing the kitchen up. Most of the work has been done by myself apart from the plastering, which I have tried but it's not for me I'm looking to get a MHVR unit into the loft and use a radial ducting system throughout the house. This forum has helped a lot, I've been reading loads of topics but I still have a couple of questions that I don't have ansers to. I had a couple of quotes in for the unit but I'm leaning towards the Domus HRXE (possibly the HRXE-H), I can really afford to spend more than 1000 pounds for the unit and this would be under budget. If someone has a better idea, I am listening. https://www.domusventilation.co.uk/ventilation-solutions/fan-range/mechanical-ventilation-heat-recovery-mvhr/hrxe I have looked at several units to see the fan settings/speeds/flow rate so I can choose wisely but I don't really understand how to read these charts. I calculated that I need a minimum extract of 52.5m3/h (48m3*0.3*3.6). Would this be enough for setting 3, 13.5l/s extract? Does the volume flow rate reffers to only extract or both supply and extract combined? What are the Pascals all about? Floor area = 90sqm total of which ground floor is 44sqm and first floor 46sqm Extract volume = 48.64m3 (kitchen/bathroom/toilet/under stairs cupboard) Supply volume = 125.72m2 (living+3bedrooms) When it comes to the ductwork, I'm been told that a rigid system is better, but the semirigid works as well. Currently looking at the Airflow Pro semi rigid system. What do you guys this, is this ok? My wife has only one requirement, that the system is quiet. My understanding is that once you increase the air velocity above 2.5m/s that's when it starts to get noisy. I was looking at the charts for the 75mm duct https://www.ribaproductselector.com/Docs/9/00139/external/COL285316.pdf on page 4 and it shows that 2.5m/s air velocity it can carry 28m3/h at 2.2Pa/m resistance. The longest pipe lenght that I need to fit is 9m. The extract for the kitchen needs flow rate of 28m3/h based on the volume of the room and I'm a bit worried, would I need to run 2 ducts to the kitchen? Does anyone know what is the maximum lenght of pipe that I can fit before I get into trouble? Enough question for now. I've attached my floor plan. Any help is much appreciated! This is a DIY project, the same as the rest of the house