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Damp toolbox part 3: Ventilation...why fresh air is so important

The headlines

The previous article looked at how people and their daily activities creates damp air in a home, and practical ideas on how to reduce the amount created.

This article explains the essential role of ventilation in getting rid of damp (and also polluted) air.

ALL experts strongly agree: Damp and air quality issues in homes can NOT be properly fixed without adequate ventilation.

They all agree that ventilation is essential to:

  • Bring fresh air in, remove stale air, and remove the many pollutants that are generated in a home.

  • Get rid of humid or damp air that can lead to black mould, damp, and associated health issues.

Air in a home needs to be completely refreshed far more often than currently happens

Even for rooms that are not used much, ventilation is essential to avoid issues.

A home CANNOT be healthy without adequate ventilation.

Although it is counterintuitive, ensuring adequate ventilation:

  • It generally improves indoor comfort.

  • Does not actually lead to worse problems in wet weather.

  • Is not expensive. I estimate around £50 a year as you will see below.


Expert opinion

The following expert groups unanimously say ventilation is essential and most important way to address all indoor air quality issues.

It is recommended that indoor air should be completely replaced with fresh air several times an hour.....far more than I think most people realise:

  • Bedrooms 2-4 fresh air changes every hour.

  • Bathrooms 6-7 fresh air changes every hour.

  • Kitchens 7-8 fresh air changes every hour.

  • Living rooms 6-8 fresh air changes every hour.

The above are the recommended figures.

Current building regulations in the UK recommend a MINIMUM of around 0.6 air changes every hour or 15 times a day (depending on room size and type).

This is often not happening in practice with some homes as low as 0.15 air changes per hour. Many UK homes are not getting anywhere near enough fresh air into them.

These problems can affect ANY age of home, including modern homes.

And finally, this screenshot from the website of one of the dehumidifier manufacturers, Ebac.


Er...but what about...?

Isn't it crazy to increase ventilation as it means losing heat?

It feels counterintuitive and somehow wrong to actually increase ventilation.

Estimating the actual cost in increased heating if you ventilate is tricky, as homes vary so much. I can't find anyone who has tried to work this out.

I've had a go though, and I estimate the average cost increase for an average UK home to ventilate properly is somewhere around £3 per week. (See the nerdy section at the end for my explanation why).

This £3 per week:

  • Is comparable or cheaper than buying and running a dehumidifier for long periods.

  • Is a lot cheaper than keeping rooms warm or the whole home warmer to keep damp and condensation issues at bay.

  • Solves damp and indoor pollution issues.

  • Provides a more comfortable and healthier home with better air quality.

On social media in December I have seen many posts by people about how much they were spending on their heating each day. This was a cold month.

They ranged in general from £3 a day up to £8 a day.

So, £3 a week as an average additional cost for ventilation doesn't seem expensive as a comparison if it solves damp and condensation issues.

Other reasons why £3 isn't actually such a crazy figure:

  • If we get rid of damp air from a home the heating doesn't have to work so hard.

  • Damp air makes us feel colder than dry air, and so more likely to turn the heating on or turn it up.

  • Ventilation in the right ways generally improves comfort rather than making it worse. My supporting article here on draughts and ventilation explains why.

But won't ventilation let in damp air from outside?

It is commonly believed that if you have a window or trickle vent open when it is wet outside it will increase the levels of humidity and damp in a home.

The other article explains why this isn't the case most of the time. It also gives you some fabulous tools to help you be confident that I've not lost the plot.

Outdoor pollution

Outdoor pollution can of course be an issue that contributes to indoor pollution. If you live in a high pollution area (such as on a busy road), ventilation may only be sensible to do (especially at the front of your home) at times of day when outdoor pollution levels are high.

If you've not yet signed up for updates, I will be publishing specific articles in the near future to help you work out when might be the best time to ventilate if you live in a high pollution area.


Geeky stuff

All costs above are based on energy costs from October 2023 assuming standard tariffs.

Why I estimate the extra heating cost of ventilation at £3 per week

  1. This is my method:

  2. The Energy Savings Trust estimates that for homes with draughty from windows and doors, the energy cost of these draughts cost around £50 per year.

  3. It is therefore it is perfectly reasonable to assume that if a home that needs more ventilation, that the cost of this will be a similar amount - £50. Spread over the five months or so of the year that heating systems are being used this works out at around £3 per week.

  4. Even if I am wrong and it is £5 and not £3 a week, I think that is a reasonable estimate and a pretty cheap way of solving these problems.

  5. I welcome any suggestions on methods of how to estimate this.

Things we ARE used to feeling or hearing about air quality

Most people will be familiar with the following:

  1. The need to have a window open in the bedroom at night. This is something that 30% of people reported doing in this survey. This is actually an incredibly good way of keeping carbon dioxide levels down in a bedroom at night, which improves sleep quality.

  2. The feeling of being in a warm room that feels 'stuffy'.

  3. The feeling of being in a cool damp room where we might feel 'clammy' when it might not even feel that cold outside.

  4. Feeling the need to 'get out and get some fresh air'.

These are all indications of indoor air that is stale or too humid for comfort.

I would argue that the above observations show we regularly experience indoor air quality issues, and from a range of sources.

And finally some trivia.......

In Nordic countries it is part of their culture to leave babies outdoors sleeping to get proper fresh air. It has been shown they sleep longer and more deeply. They do this even in sub zero temperatures!


Quick links to the other main articles on this subject.

Other supporting articles on damp:


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If you have any other suggestions for additions or changes to site content do please let me know. While I have made every effort to ensure that the information contained on this website is correct, I cannot take responsibility for errors or omissions.

All content on the site should be treated as information and not advice. You should take professional advice where appropriate to different site articles.


Mark Thompson

Get Energy Savvy - simple practical home energy efficiency information

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