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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorgravelld
    • CommentTimeMay 8th 2019
    We're changing our windows and I'd rather go with no trickle vents and have an actual ventilation "system" rather than relying on air pressure to ventilate the house.

    Before I go into the details, some constraints:

    - This is a refurb and people are living in the house
    - I can't afford HRV
    - I don't want the disruption of ducting
    - I don't like the concept of PIV - pushing out moisture laden air through holes in the fabric does not sound like a good idea

    Our current air permeability (before new windows) is 5.8 m3/hr/m2 @ 50Pa.

    Our floor area is 285m2, five bedrooms.

    We have seven wet rooms (1 x kitchen, 1 x utility room, 2 x toilet, 3 x bathrooms).

    My reading of the guidelines in the AD is that we need to provide a minimum l/s of 85 l/s on a m2 basis. If the units provide 12l/s that almost covers it. Is the calculation that simple?

    I've been looking at units like these:

    https://www.vent-axia.com/range/lo-carbon-solo-plus-selv (the HT version to ensure ventilation goes up when humidity does)

    I also believe Nuaire have similar units.

    Are these units suitable for continual extraction and will seven of them (for each wet room) be "good enough" to meet the demands of BC?

    Vent Axia weren't particularly helpful. BC are unresponsive. The window order is going in soon so I need to work this out!
    • CommentTimeMay 8th 2019 edited
    Posted By: gravelldIf the units provide 12l/s that almost covers it.

    Sorry, what units? You mean the ones you talk about subsequently?

    What are they, just continuous extract units? The web page doesn't seem to say!

    I was going to suggest the alternative to PIV, namely MEV, which is what this is I think. So yes, go for it.

    How can a product described as
    "Continuous running products, such as the Lo-Carbon Solo Plus,
    installed in all wet areas of a dwelling are classed as a wholehouse ventilation
    system and therefore only need to move the amount of air as outlined
    in table 5.1a and 5.1b of Building Regulations Approved Document F."
    not be continuous running?
    • CommentAuthorgravelld
    • CommentTimeMay 8th 2019 edited

    Yeah, the 12l/s mention refers to the VA units.

    I guess I just haven't seen anyone else do this. From what I've read, they are mostly just used as intermittent extracts, so I'm interested if people have got these passed as continually running units.

    I was just looking for some re-assurance really. Every time I try to contact BC I get very little help - I don't even understand what the process is - whether I might end up with some windows that make my house non-compliant.

    Yeah, they could be described as MEV, but not ducted.
    • CommentTimeMay 8th 2019
    Posted By: gravelldYeah, they could be described as MEV, but not ducted.

    I expect the jargon is dMEV (decentralised MEV).

    whether I might end up with some windows that make my house non-compliant.

    Worst case, you would have to cut some trickle vents into the window frames? But I can't see that being needed.

    Every time I try to contact BC I get very little help - I don't even understand what the process is

    "You can apply to your local building control authority in one of two ways:

    "a) Full Plans application: For the majority of these applications the building control team will check and ‘approve’ the plans before work starts. You’ll need to submit all drawings, specifications and, where necessary, calculations for structure, thermal, water consumption and so on. Submitting this type of application reduces the risk of contravening the regulations and helps avoid costly delays.

    "b) Building Notice: The application is ‘accepted’ when the building regulations have been met on site. However there is a risk with this option as no plans are required and work carried out may need altering or upgrading to meet requirements.

    "So if you are unsure, the Full Plans route with an approved plan will give you the assurance that you won’t be taking a risk on site.

    "You then deposit your plans and calculations which are fully checked and approved prior to commencement so you have the confidence to obtain quotes, appoint contractors and order materials based on an agreed scheme with no nasty surprises."

    from https://www.labc.co.uk/homeowners/5-steps-building-regulations-approval
    • CommentAuthorgravelld
    • CommentTimeMay 9th 2019
    Part of the problem is I've never understood what "Full Plans" means. There's no defined schema anywhere that I can find as to what should be in it, depending on the work, other than the requirement for an application form plus other documentation magic.

    Whenever I look at planning applications online the application forms always seem incredibly tersely written and with no detail at all about things like ventilation, window performance etc. You do normally get location diagrams and sections, but neither of these are relevant to this project.

    I guess it's a case of submitting stuff until they accept it - I hope they tell me _why_ they don't accept it so I know what to change.
    • CommentTimeMay 9th 2019
    Posted By: gravelldWhenever I look at planning applications online the application forms always seem incredibly tersely written and with no detail at all about things like ventilation, window performance etc.

    Those issues are building regs, not planning.
    • CommentTimeMay 9th 2019
    Who is going to install the windows? Who is going to install the ventilation? Ideally the same people? Contract one or the other to do the work including being responsible for building regs approval. If you use a registered installer that will be automatic.

    • CommentAuthorgravelld
    • CommentTimeMay 9th 2019
    No, not the same people.

    The window installers will install the windows. It's difficult enough to convince them to even remove the existing windows (is it me or are window installers a bit... 'precious'?).

    I'm meeting him tomorrow so I'll ask about this - my understanding was that under FENSA if it's a standard replacement following the standard rules (replacing windows with TVs with new windows with TVs) it's a straightforward building notice, but variations are a bit of a deviation. That said, they have to confirm all the other requirements are met (safety etc), so they must have to provide something...
    • CommentAuthorgravelld
    • CommentTimeMay 9th 2019
    Posted By: Nick Parsonsgravelld, does this help?

    https://www.dacorum.gov.uk/docs/default-source/planning-development/1---householder-leaflet-2--building-regs-mar2011.pdf?Status=Master&sfvrsn=0" rel="nofollow" >https://www.dacorum.gov.uk/docs/default-source/planning-development/1---householder-leaflet-2--building-regs-mar2011.pdf?Status=Master&sfvrsn=0
    Thanks, some good advice there, but I think this is written for new construction... I'm guessing we don't have to provide a site location plan for example, we aren't moving the house ;-)
    • CommentTimeMay 9th 2019
    Posted By: gravelldI'm guessing we don't have to provide a site location plan for example

    It doesn't say it's just for new construction; it says: 'A full plans application can be used for all types of building work'. I'm guessing you DO have to provide a site location plan because it says you have to. I expect it serves two purposes, at least:
    (1) it identifies the site, so they know which property is under consideration (as a double-check)
    (2) it identifies where the building(s) is/are on the site and therefore which clauses of various regulations will be in force.

    But there's no need to guess. Just start an online application and see what it says.

    I would also think that if you have two different contractors, it is important to get the ventilation installed and commissioned (with a commissioning certificate duly notified to BC) before you install windows without trickle vents.
    • CommentAuthorgravelld
    • CommentTimeMay 10th 2019
    Ok - thanks.
    • CommentAuthorgravelld
    • CommentTimeMay 10th 2019
    I spoke to them, they were actually helpful ;-)

    Bit embarrassing, but I had not actually asked the window installers if they were FENSA registered. Turns out they aren't, so I have to do a building notice application anyway and sort BC out to come and look.

    We have only eleven of twenty-nine apertures that currently have TVs. BC repeated the usual advice of replacing like with like and advised because our building is quite airtight (I didn't want to get into an argument about definitions, so left him thinking 5.8 m3/hr/m2 @ 50Pa was airtight) they would want TVs anyway to act as inlets for any dMEV system.

    To make the application process quicker and get the windows ordered (the factory shuts in July/Aug and we need them for the school holidays) I have decided to retain these with the new order, and gradually introduce the ventilation system separately. The window supplier reckons they are easy to block up when additional ventilation is provided subsequently.

    So I think that's what I'll do.

    This does also leave the opportunity to investigate a more radical opportunity; if we do go for EWI in a few years and we do the Larssen Truss approach I favour we could run ducting in the truss cavities (like Beattie Passive do) and actually go for MVHR.
    If there's nothing too complicated I always use a Building Notice. BCO just comes back with supplementary questions if need be. Interestingly the Dacorum advice says you need a location plan even with a BN! My LA doesn't seem to say that, and I have certainly never provided one. However nearly 40 years ago when I split a bedroom to form bedroom and bathroom I was required to do a full plans app and provide a location plan.
    • CommentAuthorgravelld
    • CommentTimeMay 10th 2019
    Oh yes - I asked about the location plan, they said not to bother and just put our address in.
    85l/s is a lot of ventilation, have you worked out how much energy it will use each year to heat that much air? Might be worthwhile to go straight to MHRV?

    If the ducts are a problem, others have used single room MHRV units in place of extractor fans, I have no experience with these myself.
    • CommentTimeMay 10th 2019
    Single room MHRV has been good for us, eg:



    • CommentAuthorgravelld
    • CommentTimeMay 13th 2019
    Posted By: WillInAberdeen85l/s is a lot of ventilation, have you worked out how much energy it will use each year to heat that much air? Might be worthwhile to go straight to MHRV
    I know it's a lot, but AIUI the regs are very safety-first. My plan is to simply turn it down (many of these units can have different rates) and use humidity and CO2 monitors to make sure I'm not doing anything silly.

    SRHRV wouldn't be so great in bathrooms imo because of the lower temperature of the air input but that probably depends on where it is sited and where the draught runs.

    I actually just brought one of these to test in one of our en suites: https://www.greenwood.co.uk/product/153/unity-cv2gip . They make a newer one with NFC and app based wizardry but it appears to be a similar product and I don't really need the app stuff.
    • CommentAuthorkmach
    • CommentTimeMay 31st 2019
    The low energy building consultant we spoke to recommended Aereco: https://www.aereco.co.uk/
    It doesn't require for the building to be airtight especially if you're not doing a deep retrofit although the system would need trickle vents in the windows and background ventilation. The company was responsive and helpful as I asked a lot of questions. In the end though, we decided to go for the MVHR since we're doing a complete renovation.
    • CommentAuthorHoveTom
    • CommentTimeSep 5th 2019
    I am considering Aereco in my bungalow Conversion and possibly the Velux active system I just posted a equestrian about separately.

    I can confirm Aereco are very helpful on the phone. They have air inlets which come through the walls or they sell a separate inlet which you can fit into the same slot a standard trickle vent comes in when you get your new windows. You just pull them out and screw their inlet in. They have extracts in all the wet rooms. The air isn’t filtered and no heat is recovered but the system is designed for a house which isn’t particularly air tight.

    Does anyone have any practical experience of this system?
    • CommentAuthorgravelld
    • CommentTimeSep 10th 2019
    Aereco were very good with me too - I think I originally discounted them because it wasn't *quite* cost effective enough. Although they were cheaper than any other of the full-on "systems".
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