How to Stop Condensation in Your Loft

Roof Care & Maintenance
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How to Stop Condensation in Your Loft

Although it may seem worrisome discovering damp in your loft, it is a pretty common problem that many homeowners face. In fact, it is estimated that at least 1 in 5 properties across the UK suffer from excess condensation and moisture levels, especially throughout the loft space. But what exactly causes condensation in your loft? And how can you go about fixing it?

Thankfully, with modern design and materials, there are now a multitude of different methods and innovations you can utilise to minimise any condensation issues with relative ease. In this handy article, we will talk you through the ins and outs of loft condensation, highlighting the signs you need to look out for as well as the practical fixes to prevent further damage.

Table of Contents

What Causes Condensation in the Loft?

A good place to start when figuring out how to stop condensation is discussing what actually causes it in the first place. Although condensation and excess moisture can build up at any time of the year, it is a problem most commonly noticed throughout autumn and winter.

When warm, moist air moves up into the loft space and meets a cooler surface, it cools down quickly and expels the excess water as droplets on the surface. During the colder months, we are less likely to introduce fresh air into our homes, utilising central heating and fires to warm up the space. This traps moisture inside and heightens condensation levels.

There are a multitude of reasons why excess moisture may be building up in your loft, often caused by innovations we think are aiding our properties.

Loft Insulation

Loft insulation is great for warming your home, improving energy efficiency, and even lowering your utility bills. However, in some cases it can cause problems with damp, condensation, and moisture damage. Loft insulation can often limit your homes ability to ‘breathe’.

You may think that the more insulation you install the better, however adding additional insulative material may restrict natural air circulation. This will mean that although the rooms below will be heated to a warmer temperature, the actual loft space remains pretty cold. Hot air rises, so as it does and meets the cold surfaces in the loft, the water condenses.

Despite this, there is no need to rip out all of your insulation and live in discomfort all through winter. With proper installation techniques and usage of correct insulative and ventilation products, you can still achieve the warmth your home requires without the excess moisture build up.

Blocking the Loft Vents

Adequate ventilation is highly important to regulate air flow throughout the loft space. Dependant on the age and type of property you live in, the level of ventilation your loft has may vary. For example, older homes could have minor tile vents or even no ventilation at all. In most modern properties, you will notice ridge and eaves ventilation, fitted in a continuous length to regulate airflow through the loft.

Many of us like to utilise our loft space as extra storage for boxes and other belongings. However, it is actually advised by the National House Building Council that you do not use your loft as storage as this can greatly effective the level of ventilation throughout the space. Without realising, you may be completely blocking off the loft vents and restricting the air flow. This restriction causes condensation to form, not only effecting the loft structure itself but also potentially damaging the items that you wanted to keep safe.

Hot Water Tanks

It is not uncommon throughout the UK to find properties with hot water tanks located in the loft space. Although practical in terms of space saving, without realising your water tank could actually be causing some significant moisture damage by leaking steam through improperly sealed lids. This leaking steam quickly turns into condensation, settling through your loft space.

It is vital that you check your hot water tanks at least once a year, especially in the months leading up to autumn and winter. It is an easily fixable problem that so many homeowners may overlook, leading to more expensive damage down the road.

Wet Trade Building Materials

In newly built homes, it is not unheard of for wet trade materials such as concrete, plaster and mortar to trigger some moisture issues within the property. Materials such as this are mixed with water, which then causes high volumes of excess moisture to expel into the surrounding area whilst drying. This moist air triggers condensation by hitting a colder surface then condensing into droplets and causes damp.

If wet trade building materials have been newly used in your property, it is vital that the home is well ventilated, especially in the first few years of use.  

Un-Insulated/Poorly Fitted Loft Hatches

Warm, moist air can easily travel through poorly fitted, unsealed or inadequately insulated loft hatches into the loft space. As this humid air enters, it then meets the cold surfaces within the loft and condenses, creating pools of moisture. This excess moisture can then trigger expensive and potentially dangerous problems such as damp, mould and rot.

Day-to-Day Life

Without realising it, the activities we carry out during our day-to-day lives can actually be causing a significant amount of the condensation that is found up in the loft space. For example, even just as we breathe, we release hot, moist air which has the ability to condense. You may be surprised to find out that on average, as much as 14 litres of water vapour is released into the air every day in just a 4 person household.

So apart from breathing, what else are we doing everyday to contribute so much water vapour? Well, according to Endsleigh, just taking a bath or shower without using an extractor fan or opening a window can produce up to 2 pints of moisture. Cooking or using a kettle can generate up to as much as 6 pints whilst washing and drying clothes inside is another significant contributor. Without adequate ventilation, moisture escapes from the wet clothing material, moving up through the home into the highest point (your loft space) and causing condensation.

Lack of General Home Ventilation

Continuing on from our previous point, lack of ventilation throughout the entire home, not just the loft, can be a major reason why you are finding so much excess moisture at the top of the house. It’s no surprise that as the weather gets chillier, its far less common to see homeowners cracking open windows for a gust of crisp winters air. However, opening windows is a fundamental outlet for ventilation and without it, you are trapping a lot of hot, moist air inside with nowhere else to go but upwards.

Some homes do actually have other forms of ventilation such as wall and window vents, however homeowners may have them closed without realising or have large pieces of furniture blocking the air circulation.

Leaks & Damages

A less spottable but equally problematic culprit for condensation build up could be leakages and existing damages to your loft. If you believe there may be any hindrance or damage to your loft, roof or plumbing pipework, get them checked out and evaluated to ensure everything is in working order.

What Issues Can Damp in the Loft Cause?

So we know what causes condensation in the loft, but what’s the really the big deal? Well, actually a build-up of damp and moisture in your loft space can not only lead to expensive damages and repairs, but it can also have a negative effect on the health of the property’s inhabitants.

When left untreated to get worse, moisture build up in the loft space can lead to black mould, damp, decay and rot. This can hinder your insulative materials, weaken the structural integrity of the loft, damage your belongings and trigger respiratory problems, infections, allergies or even asthma.

Thankfully, when caught soon enough, you can easily avoid such dangers as this and restore your loft space to an effectively functioning and imperative part of the home.

Warning Signs to Look Out For

It can be tricky to know what to look for when it comes to diagnosing condensation issues. Here are a few tell-tale signs that your loft space may be experiencing some built-up moisture:

  • Trickles of water moving down walls
  • Damp/wet insulation material
  • Damp/wet wood
  • Water marks & dark stains
  • Damp, damaged or wet roof sheathing
  • An unexplained musty smell
  • Visible moisture on surfaces
  • Visible rust or mould

How Do I Fix Loft Condensation?

If you’ve reached this section and are concerned that you may already have an issue with condensation in your loft, do not worry. You have a way to fix the problem, however it is advised that you act as quickly as possible.

Inspecting Vents

The first step is to give your loft space a thorough inspection to ensure you have the clearest picture of what is causing the moisture issues. Carefully check for obvious signs that may be triggering water ingress into the roof space such as cracked or broken roof tiles, cracked leadwork or leaking pipes/guttering.

If all is in order, move on to evaluating the effectiveness and condition of your ventilation and insulation. Have a look around and assess how well ventilated your loft space is. If you can spot existing vents within the loft, ensure that are completely unobstructed. Make sure that any boxes or storage items are moved at least 5-10cm away from vents to allow adequate air circulation.

Replacing Insulation

Next, inspect your existing loft insulation. If the material seems to be in good condition and working as it should, then there is no need to replace. However, if upon evaluation you find moisture damage, pests, breakages or just feel like it is unfit for purpose, consider swapping out for a newer, more breathable alternative. Also don’t forget to install a vapour barrier to enhance protection against moisture ingress.

Which Insulation Should I Choose?

One of the most effective forms of loft insulation recommended for modern homes is natural sheep’s wool insulation. Sheep wool can absorb up to 33% of its weight in moisture without affecting its insulative performance or quality. The core of the fibre is hygroscopic which means it can absorb water vapour easily, preventing condensation from even becoming an issue in the first place. It is also a highly sustainable, environmentally-friendly option so is perfect for those looking to create a more eco-conscious home.

Increasing Ventilation

There are a variety of vents you can install that will effectively increase air circulation and ventilate your loft space.

Roof Tile Vent/Roof Slate Vent

A common and highly popular ventilation solution, roof tile and slate vents are easy to install, effective for purpose and blend seamlessly with the rest of your roof design. Although similar in appearance to your standard tiles/slates, these instead incorporate slim vents which permit a passage of circulating air into the loft space.

The innovative design blocks moisture from entering into the space below through the vent so you can keep your loft dry and clean.

Felt Lap Vent

Felt lap vents are often fitted to older style roofs with bitumen felt undersarking. This easy to fit product is inserted on the inside of the roof and is very effective at minimising moisture build-up in the loft space.

Fascia, Soffit & Eaves Panel Vents

These roof vents are typically fitted on the inside of the roof and are available in a multitude of styles, colours, materials, sizes and finishes to perfectly accommodate your roof type. They are very affordable for homeowners and produce effective results in lessening moisture build-up throughout the loft space. It is best to fit vents such as this on brand new roofs or whilst upgrading an existing roof, unless the condensation issues are urgent.

Over Fascia

Over fascia vents provide low level ventilation but are less simple to fit DIY. The units are nailed over the top of the fascia board, creating a continuous length of venting. They typically also include a mesh grill which blocks out insects, bugs and small wildlife from entering the roof space.

How Do I Prevent Loft Condensation in the Future?

Now you have successfully fixed the damp and condensation in your loft, it is important to take the necessary steps to prevent it from reoccurring in the future.

Kitchen & Bathroom

As we know, activities such as cooking, bathing, showering and boiling water can generate some significant moisture within the home. Thankfully, there are very simple ways to reduce this build-up and avoid hot, moist air travelling up to your loft space. Practical methods include:

  • Keeping windows open during and after showering, bathing, cooking etc
  • Installing and using extractor fans
  • Using a dehumidifier
  • Taking cooler showers/baths


Regularly inspecting and evaluating your insulative materials is a key way of combatting future condensation issues. Often, a simple imbalance between insulation and ventilation can be a root cause of moisture-build up but can be very easily combatted if stability between the two is maintained. Any time you consider upgrading or changing your insulation, make sure you keep in mind the levels of ventilation you have within the loft too to keep both up to the same level of performance.  

Washing & Drying

During autumn and winter, it can be very tempting to turn up the radiators, bring out the clothes airers and dry all laundry inside the house. Although this will often get your clothes dry quicker, research shows that drying clothes in the house can increase moisture levels by up to 30%.

This moist air will travel upwards and has the potential to create condensation problems in your loft space. Where possible, it is advised to utilise washing lines and dryers outside where weather permits. If inside drying is the only option, then you must ensure the space is correctly ventilated, opening as many windows and doors as possible to effectively circulate fresh air.

Roofing Upgrade

You will often find that in older roofs, the existing roofing felt material restricts moisture and vapour from passing through it, therefore increasing the level of condensation build-up. There is no quick fix for this as the process does involve removing all roof tiles/shingles and completely replacing the old felt with a roof breather membrane or vapour barrier.

However, if you are having consistent moisture problems that don’t seem to be going away, this may be a good time investment to make to solve the problem and prevent future costly damage down the line.

Warm Roof

Another effective way to minimise condensation is to convert your roof into a “warm roof”. This involves fitting the insulation between your roofing tiles and battens instead of above the ceiling. This changes the roof space from ‘cold’ to ‘warm’, creating less active conditions for the formation of condensation. Creating a warm roof with natural sheep’s wool will increase effectiveness and add breathability to minimise moisture build up further.  

To Conclude

Condensation in the loft space can be an inconvenient and potentially costly issue. However, when treated quick enough with future preventions in place, you can avoid this impractical build-up of moisture whilst running your home comfortably and efficiently all year round.

If this post has inspired you to take a look at your own loft space, why not have a browse through our high-quality range of insulation and ventilation products, available at Roofing Megastore now. Alternatively, for any other questions or queries, don’t hesitate to get in touch with our friendly customer service team who will be more than happy to help. Simply give them a call on 01295 565565, email [email protected], or leave a message in our handy live chat.

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