Over the holidays we had occasion to have13 adults in our kitchen. No trickle vents , just a heat recovery extractor bringing in fresh air on boost and maintaining the temperature. When our guests went home I turned off the extractor. Trickle vents would not have coped with the fresh air demand and are not readily switched off. Hope this example helps.
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My MVHR is always on in a type of background ventilation mode, if our house suffered from dampness that would help deal with the background humidity. Then it increases flow rate automatically as humidity rises. There is a manual boost option that can be used as required.
Trickle vents would interfere with both effective ventilation and heat recovery.
There is an âalmost offâ mode for holidays, which I hardly use, so that indoor pollutants donât build up in our absence.
However @pottyone72âs recent posts related to those unable to afford MVHR or who wouldnât be permitted to interfere with the landlordâs assets even if they could afford to.
I donât believe this has ever been considered. I would like to be shown otherwise but if they have tried there have been recurrent demonstrations of incompetence.
I have my reply from my MP, who I have to say I find responsive and interested in the matters I have shared with him about my home retrofit and energy efficiency.
Here is his response below.
Dear Mike Kane,
A constituent expressed concern about requirements to install trickle vents in homes. They expressed concern that they were not suitable to manage moisture in their home. You asked for help in responding to them.
Summary
In short: there is no requirement to fit trickle vents in all existing homes. Building regulations, which apply to new builds and some building work on existing homes, say there should be background ventilation. This can include trickle vents, but they are not mandatory. If your constituent is planning relevant building work to their home, they may need to comply with current building regulations, but trickle vents will not be mandatory as long as they meet ventilation requirements in another way.
For further information on energy efficiency, ventilation and moisture resistance requirements for new homes, see section 8 of the Library briefing on Health inequalities: Cold or damp homeshttps://commonslibrary.parliament.uk/research-briefings/cbp-9696/(February 2023). For further information about the building regulations in general and how they are enforced, see sections 1 and 2 of the Library briefing on Building regulations and safetyhttps://commonslibrary.parliament.uk/research-briefings/cbp-8482/ (June 2023).
Please note that building regulations are a devolved matter and this response only covers England.
Background: Building regulations
The energy efficiency, ventilation and moisture resistance of a new home when it is constructed or when an existing home is significantly altered are regulated by the building regulations (under the Building Act 1984https://www.legislation.gov.uk/ukpga/1984/55/contents and the Building Regulations 2010https://www.legislation.gov.uk/uksi/2010/2214/contents).
Work on âcontrolled fittings or servicesâ (such as replacing a boiler or a window) is also considered building work for the purposes of the building regulations.
Building regulations apply only at the time when building work is taking place; standards for existing homes will therefore usually depend on when they were built. There is no requirement to retrofit homes to comply with new building regulations (unless relevant building work is carried out).
Requirements for ventilation and moisture control
Part C of Schedule 1 of the Building Regulations 2010https://www.legislation.gov.uk/uksi/2010/2214/schedule/1 deals with moisture control, Part F sets standards for ventilation and air quality and Part L deals with the conservation of fuel and power. They set standards that need to be met (for example, energy performance standards) rather than the way they need to be achieved (for example, by using a specific type of insulation). They do not prescribe which technologies, materials or methods should be used.
To provide guidance on ways to meet the requirements set out in the Building Regulations 2010, government publishes Approved Documentshttps://www.gov.uk/government/collections/approved-documents. However, there are other ways to meet the requirements set out in the Building Regulations 2010 than following the examples and solutions set out in the Approved Documents.
Updates to ventilation requirements
The government updated the energy efficiency standards and ventilation requirements set out in Part F and Part L of the Building Regulations in 2021https://www.legislation.gov.uk/uksi/2021/1391/made. The changes took effect on 15 June 2022. The updated requirements apply primarily when building new homes but also when undertaking work on thermal elements in an existing home, for example, when installing insulation. When building work affects the ventilation of a home, it should comply with updated air quality standards or, at least, meet the standards that existed prior to the works taking place (see Regulation 4 of Building Regulations etc. (Amendment) (England) Regulations 2021https://www.legislation.gov.uk/uksi/2021/1391/regulation/4/made).
Alongside the update to the Building Regulations, the government also updated the relevant Approved Document. Approved Document Fhttps://assets.publishing.service.gov.uk/media/61deba42d3bf7f054fcc243d/ADF1.pdf (PDF) recommends that all dwellings should have a means of âwhole dwelling ventilationâ, such as background ventilators (for example, trickle vents) (para 1.23). Supporting guidance on frequently asked questionshttps://www.gov.uk/guidance/approved-document-f-volume-1-dwellings-frequently-asked-questions clarifies that there is no requirement for trickle vents to be installed in all buildings and âinstalling a background ventilator through a wall [âŚ] can be an acceptable route to complianceâ for new builds.
Further updates in 2025
To meet its net zero target by 2050, the government will introduce further updates to Part L (conservation of fuel and power) and Part F (ventilation) of the Building Regulations for new builds from 2025, under the Future Homes Standard. The government initially consulted on the standardhttps://www.gov.uk/government/consultations/the-future-homes-standard-changes-to-part-l-and-part-f-of-the-building-regulations-for-new-dwellings in 2019 and is currently carrying out a consultation on the technical specification of the standardhttps://www.gov.uk/government/consultations/the-future-homes-and-buildings-standards-2023-consultation (closes 6 March 2024). Neither consultation mentioned a requirement for trickle vents.
I hope this helps but please let me know if you require further information.
Best wishes,
Felicia
Library Researcher
Science and Environment Section
House of Commons Library
House of Commons, Palace of Westminster, London SW1A 0AA
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From: HCLibrary
Sent: 12 January 2024 16:30
To: Mike Kane <mike.kane.mp@parliament.ukmailto:[mike.kane.mp@parliament.uk](mailto:mike.kane.mp@parliament.uk)>
Cc: CROMARTY, Hannah <cromartyh@parliament.ukmailto:[cromartyh@parliament.uk](mailto:cromartyh@parliament.uk)>
Subject: Window trickle vents, airtightness and ventilation (Case Ref: MK50634) - ID 838091
Dear Mr Kane,
Thank you for your request. Your unique request ID number is 838091.
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From: Mike Kane <mike.kane.mp@parliament.ukmailto:[mike.kane.mp@parliament.uk](mailto:mike.kane.mp@parliament.uk)>
Sent: 12 January 2024 16:12
To: HCLibrary <HCLibrary@parliament.ukmailto:[HCLibrary@parliament.uk](mailto:HCLibrary@parliament.uk)>
Subject: FW: Window trickle vents, airtightness and ventilation. (Case Ref: MK50634)
Dear Colleague
Case Reference: MK50634
I have received the email appended below from a constituent.
I would be grateful for your observations and advice on this matter.
Best wishes
Mike
Mike Kane MP | Wythenshawe and Sale East
+44 (0)161 499 7900
House of Commons, Palace of Westminster,
London SW1A 0AA
MP Website: Mikekane.org
Facebook: Mike Kane
Twitter: @MikeKaneMP
In addition to all of the information above supplied via government, legislation and building control - this is the question that still remains in my mind âcan the breathable qualities of lime plaster deliver enough ventilation for me not to need trickle vents ?â
Is there evidence to support this. It feels like a fair and logical enough question to ask â
When your house was a new build on someoneâs farm there would have been breathable walls, but breathable does not equal ventilation.
(You have seen my post on airtightness and breathability.)
Ventilation would have come from around window casements, doors, coal shutes and chimneys. Most, if not all, of those options are lost in a retrofitted home so therefore alternative ventilation needs to be provided to meet the requirements of the inhabitants, any combustion (eg. cooking) that might occur and for rapid removal of clouds of high humidity caused by use of hot water.
You have extractors already and are hopefully about to fit the bathroom MVHRđł.
Where is your fresh air coming from? As you airtighten your house you need to plan for this. The most energy efficient answer is to use MVHR. The least energy efficient is a trickle vent or air brick. Take your pick.
I know that finances are a limiting factor so I think I would plan where I want future MVHR units, make appropriate holes and fit them with one way louvres to control the direction and possibly rate of airflow, then fit the MVHR as you are able to do so. Meanwhile they will satisfy your ventilation obligations in so far as natural ventilation can ever do so.
Hi Carla, Well done for getting clear guidance on the ever changing building regulations. Please remember that all modern windows have a double locking mechanism that allows them to effectively act as large trickle vents (full opening), and you have the choice as to when and how long you have these open.
(Building regs) They set standards that need to be met (for example, energy performance standards)
rather than the way they need to be achieved
(for example, by using a specific type of insulation). âThey do not prescribe which technologies, materials or methods should be usedâ.
You therefore already have the trickle vent mechanism built in and do not need additional holes in your window that diminish overall energy conservation performance.
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That makes sense and avoids drilling holes in your walls before you are ready. I donât know why I didnât suggest it myself. 
We are here to share and learn. This is the locking block that allows venting
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