The Cheapest & Easiest Way to Cure Loft Condensation

“This one product will get rid of condensation in lofts”

Created by: Daniel Woodley. Posted to: Off Topic. Published: 25th of July 2022.

If I told you that you could get rid of loft condensation in a matter of minutes with a product that any DIYer can install and all for about £20, would you believe me?

Well it’s true and I know because I worked as a roofer for 17 years and have fitted this product to hundreds of lofts but you don’t need to pay for a roofer. If you are fit enough to get into your loft and you have a traditional home (with insulation on the floor of the loft), you can solve the condensation problem yourself.

In a hurry?

I recommend these loft vents which can be purchased via Amazon.

But keep reading to find out how to install these vents and also why and how loft condensation forms.

My Video

Watch me fit this product in my loft and listen to me explain how and why condensation forms in the first place:

What Causes Condensation in Lofts?

Every occupant of your home produces moisture from:

  • Breathing.
  • Sweating.
  • Cooking.
  • Bathing.
  • Drying clothes, etc.

Warm air pulls this moisture upwards and into the loft where in theory, it shouldn’t cause a problem.

However, when the loft is cold (from late autumn into winter and spring), the underside of the roofing felt and the timbers will be cold.

As the moist, warm air comes into contact with the cold surfaces in the loft, it condensates, just like it does on car windscreens in the winter or on cold taps in the house.

Next time you have a hot bath, look at the cold mirror, window or tap; condensation forms here just as it does in the loft.

The Solution

The most effective way to cure loft condensation is to install ventilation so a breeze can enter the loft and pull the moisture out of the loft into the atmosphere (this method works for most lofts in the UK but not “warm roofs”).

There are several ways to achieve this, the most common being loft and roof vents:

Loft vent to ease condensation

Loft vents are cheap and easy to install from inside the loft space – perfect for DIYers

Roof tile vent

Roof vents cost more and should be installed by a professional from outside the roof 

How to Install Loft Vents

Installing these loft vents couldn’t be easier, they simply slip in between the felt overlap as shown in the image below:

Installed vent

No tools or specialist equipment are needed to fit these vents and you don’t need access to the exterior of the roof either.

A typical 1 bed home will require about 6 vents (3 front and 3 rear)

A 2-3 bed semi-detached home will require around 10 vents (5 front and 5 rear)

Larger homes or those with multi-sided roofs will require more vents but start with no more than 10 vents and monitor the condensation.

Don’t forget, it can take some time to clear, especially if there’s no breeze.

10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow
10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow
10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow
Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow

I Found 1500 Reviews Online – Here’s How Others Rate These Vents

As part of my research into the best products to get rid of loft condensation, I looked at tens of thousands of reviews and ratings online for this and similar products.

I know these vents work but I wanted to see how others rate them.

As of July 2022, there are 1586 reviews on Amazon.

91% of consumers rated these loft vents either 4 or 5 stars out of 5 which is very high.

Only 2% of reviewers rated the vents 1 star out of 5 which is very low.

I think these stats speak for themselves and I couldn’t find any issues worth reporting or investigating further.

11 Questions About Loft Condensation Answered

During my 17 years working as a roofing contractor, I was often asked questions about loft condensation; here are the answers to the most common questions:

    Will My Heating Bills Go Up If I Install Ventilation? 

    No, in most lofts, the insulation is placed on the loft floor. Your heating bills won’t be affected if the vents are installed above this.

    I Never Had Condensation Before, Why Has It Formed Now?

    Condensation forms in colder conditions, and it could be that you only entered the loft when it was warm, and none was present.

    Also, if you add extra insulation to your loft, the warmth will stay trapped in the home below, meaning the felt and timbers in the loft will be colder. The colder the surfaces in the loft, the more condensation will form.

    Boarding out a loft can also cause condensation for the same reason – by trapping heat in the home, the loft becomes colder and more susceptible to condensation.

    Condensation In My Loft Comes and Goes. Why?

    This is normal and, in most cases, is nothing to worry about. You should only be concerned if it persists and causes mould, dampness or rot.

    The roof or loft vents require a breeze to pull the moisture out of the loft, so, on calm days, you may experience more condensation.

    You may also notice more condensation when the outside temperature drops – it’s perfectly normal and should disappear when it warms up and should ease when there’s a breeze, provided you have sufficient ventilation.

    Do Double Glazing Windows and Cavity Wall Insulation Cause Loft Condensation?

    Old drafty timber windows allow moisture to escape from the home, and if you replace them with airtight modern windows, the moisture levels in the home and also the loft will increase, and condensation is more likely to form.

    Cavity wall insulation keeps homes warmer for longer, and as warm air holds more moisture than cold air, you may notice a slight increase in loft condensation after installing cavity wall insulation.

    Why Am I Experiencing Loft Condensation In The Summer, When It’s Warm?

    This is not normal and should be investigated further.

    It could be caused by:

    • A roof leak.
    • A pipe leak.
    • Loose or faulty extractor fan or fan ducting.
    • Hot water tanks in the loft failing (broken lid, defective thermostat or heating element etc.).

    Is It Normal For a Loft To Smell Musty?

    Lofts shouldn’t be damp or smell musty and such issues could be a sign of a roof leak, ventilation issues or other faults that will need investigating.

    Can I Install Vents To a “Warm Roof”?

    A “warm roof” is when the insulation is placed directly under the roof tiles and the loft is usually the same temperature as the rest of the house.

    If your loft insulation is placed on the floor of the loft, you have a “cold roof” and the loft will usually be colder than the rest of the home in the winter.

    Loft vents should only be installed on cold roofs and never to warm roofs.

    I Have Condensation In My “Warm Roof”. What Should I Do?

    This is usually due to missing insulation under the roof tiles which causes cold spots where condensation forms. This should be investigated by a professional roofer if you can’t see any obvious failure of the insulation.

    Will Loft Vents Cause Leaks?

    The felt on most roofs is overlapped and not airtight, these vents just open the overlap slightly to create an airflow into the loft. If correctly installed, there is no way that these vents can cause a roof leak.

    Are There Any Alternatives To Loft Vents?

    Roof vents are just as effective but must be fitted from the exterior of the roof and access equipment such as scaffold might be needed.

    Mechanical ventilation such as an extractor fan would be effective but these are rarely found in lofts and consume electricity.

    Will A Vapour Barrier Help?

    A vapour barrier is a plasticky felt-like material that is laid above the ceiling plasterboard and is designed to let air and heat into the loft while blocking moisture/vapour.

    A correctly installed vapour barrier can stop moisture from getting into the loft in the first place but they are difficult and costly to retrofit into an existing home and are best suited to new builds, extensions and major renovations.

    An incorrectly installed vapour barrier can cause condensation spots and even the pooling of water and the humidity level in the house can skyrocket.

    Modern types of vapour barriers allow some moisture through but not so much that condensation will be a problem.

    99.9% of loft condensation cases can be resolved to an acceptable level by improving the ventilation rather than retrofitting a vapour barrier.

    Loft Condensation Checklist

    Here’s a checklist for anyone experiencing loft condensation:

    • Is it unusually cold outside? It’s normal to see some condensation in the loft during cold snaps.
    • Is it warm outside? It’s very unusual to see condensation in a warm loft. Check for roof leaks, burst pipes or faulty hot water tanks, lids, thermostats or heating elements etc.
    • Is it unusually calm with no breeze? Wind is needed to flush out moisture via vents. If it’s unusually calm, wait a day or two and see if the condensation clears on its own.
    • Double-check your loft insulation isn’t blocking any existing vents at the corners of the loft (where the roof meets the loft floor, there should be a gap).
    • If you have boxes and possessions in the loft, make sure they aren’t blocking the existing vents.
    • Have you recently upgraded your loft insulation or boarded out your loft? Your house may be warmer but your loft will be colder and more susceptible to condensation, try adding a few loft vents to improve ventilation.
    • Are you creating excessive amounts of moisture in the home? Showering or bathing without opening the window or using an extractor fan can cause moisture levels to increase, as can washing clothes on radiators etc. The condensation will only form when the temperature in the loft drops so it may not be obvious that the lifestyle of the occupants is contributing to the problem.
    10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
    Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow
    10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
    Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow
    10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
    10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
    Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow
    Pack 25 Roofing Felt Lap Vent Stops Loft roof Condensation / Attic Space Ventilation Airflow

    Author: Daniel Woodley

    Thanks for reading my guide to condensation in loft. My name is Daniel Woodley and I first published this article on the 25th of July 2022 here at DIY Gardening in the Off-Topic section.

    Discover more helpful hints and tips from me over at the blog.

    I’m a former roofer and a keen amateur gardener who’s trying to reduce his reliance on harmful weed killers and other chemicals but I accept there is a place for them in some limited scenarios.

    I also enjoy growing vegetables and fruits, as well as my herbaceous borders and small container courtyard.

    More About Daniel Woodley

    Danny Woodley

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