Condensation on metal-roofed homes is a common challenge. Warm air rises and hits the cold roof (especially at night), condensing into water droplets drip to the ceiling and sometimes the floor below.
Unfortunately, roof condensation can be very costly. Common issues include ceiling damage, attic rot, insect infestation, mold, and mildew.
So we’ve developed this guide to help you understand how anti-condensation roof paints work and how to use them to prevent roof condensation problems.
What’s the best paint to stop metal roof condensation?
Tikkurila Grafo Therm is the best paint to stop metal roof condensation. It is a one-component water-based coating for steel structures, metal roofing sheets, and other metal surfaces where condensation occurs. Additionally, you can use it for mineral walls and ceilings.
What Causes Metal Roof Sweating?
Roof condensation forms when warm indoor air hits a cold metal roof at zero degrees Celcius or lower.
This initially seems unlikely. But remember that roof temperatures can be up to 15 degrees colder than outdoor temperatures at night. So, a 15-degree Celcius night leaves the roof at zero degrees.
Yet, according to the NCDC, the average night temperature in the US is 44.3 degrees Fahrenheit (6.8 degrees Celsius). This means that most of the country experiences sub-zero metal roof temperatures at night for the better part of the year – creating perfect conditions for condensation.
Often, the rising moist air is trapped between the underlayment and the metal roof or within the attic. Then it condenses at night when the roof temperature drops below the dew point. This happens on all metal roofs, including corrugated metal roof structures.
Signs of Metal Roof Condensation
The signs of roof condensation are visible throughout the house. For instance, it occurs on rafters, around windows, and floor joists. Additionally, condensation can form around bathroom vents and between the attic insulation and the underneath ceiling.
Water pools or condensation marks around the bathroom fan can result from roof condensation forming in the air ducts due to roof condensation. Similarly, condensation on the rafters can flow down the walls to the floor, leaving condensation trails on the walls and ceiling.
Unfortunately, sometimes you may not even notice the condensation problem in the early days as the ceiling absorbs the dripping condensate. In this case, keep an eye out for the following signs;
- Unexplained water stains
- Wood floor rots
- Electrical issues (short-circuiting)
- Mold and mildew problems
Dangers of Roof Condensation
Condensation is initially harmless. It causes a few water droplets that never reach the living areas, and the condensate dries up when temperatures rise during the day. However, the problem can become dangerous real fast. Common medium and long-term risks include;
- Mold and mildew: Dampness around the affected areas easily attracts mold and mildew, which can spread to other parts of the home.
- Rotting wood structures: Before you know it, the water may affect wooden structures on the roof and walls, causing wet rots.
- Health issues: Mold, mildew, and rot pose serious health issues. They can cause nasal irritation, trigger allergies, and cause lung infections.
Can Metal Roof Condensation Damage the Home?
Unfortunately, yes. If left unaddressed, drip condensation can cause water pools in the ceiling, ultimately damaging it. Additionally, trapped condensate can damage roof underlayment, trigger rusting, and weaken walls and floors.
The worst part is that you may only catch the problem when it’s too late. When this happens, you may need extensive repairs, including replacing some wall sections.
What’s Anti Condensation Paint?
Anti-condensation paint is a type of paint with extra thermal insulation properties. The paint’s thermal insulation properties alter temperatures on the roof surface, effectively repelling warm air. This reduces the risk of condensation.
In addition, an anti-condensation paint is an elastomeric coating (it contains elastomers). An elastomer is a naturally occurring compound with high viscosity and elasticity, almost like rubber. Additionally, elastomers are highly water-repellent.
Waterproof elastomeric paints reject water completely, while water-resistant options protect against liquids.
How do Anti-Condensation Paints Work?
The process is simple – you apply the anti-condensation paint where you want it most, and it repels warm air while resisting water.
For instance, apply anti-condensation paint on both sides of roofing sheets to cure metal roof sweating. Then install the sheets normally. Once in place, the paint creates a water vapor barrier and repels the rising warm air, thwarting avenues for condensation.
Does Anti-Condensation Paint Work on Metal Roof?
Yes, anti-condensation paint works excellently for metal roofs – provided you choose the right paint. The paints stick strongly to the surface, repelling warm air and moisture for a dry roof with minimal dripping water problems.
However, beware that not all anti-condensation paints are ideal for metal roofs. For instance, although it’s highly effective, PermaSeal anti-condensation paint solely targets walls and ceilings.
Also of importance is surface preparation. You must properly prep the surface to create an airtight seal. Otherwise, the paint begins to come off within a few weeks.
How Effective are Anti-Condensation Paints?
Anti-condensation paints reduce metal roof sweating by 60% or more. The exact figure depends on the type of paint and project conditions.
For instance, it’s a big challenge to eradicate metal roof condensation in hot and humid climates. Similarly, poor ventilation makes indoor humidity control difficult. So, a 60% condensation reduction in such environments is a big success.
On the other hand, you can almost eliminate metal roof condensation in mild climates if you combine anti-condensation paints with other humidity control measures.
What’s the Best Anti-Condensation Roof Paint?
Unfortunately, there are few metal roof anti-condensation paints. Our recommendations for US homeowners are Tikkurila Grafo Therm from Rawlins Paint and Roof Guard from Hy-Tech Thermal Solutions.
1. Tikkurila Grafo Therm
Tikkurila Grafo Therm is a one-component water-based elastomeric coating for steel structures, roofing sheets, and other metal surfaces like metal sheds. It forms a strong elastic membrane that insulates from heat and boasts excellent moisture absorption capacity.
Also, evaporation occurs faster when you paint metal roofs with Grafo Therm as it breaks water surface tension, spreading the moisture over a larger surface area.
In addition to its condensation protection properties, Tikkurila Grafo Therm provides vibration and acoustic damping when you apply a thick layer. It dries to the touch in 1-2 hours in normal temperatures, forming a beautiful matt finish.
Pros
- Insulates metal surfaces from heat
- Increases surface evaporation
- Dries in one to two hours in normal weather
Cons
- It’s strictly for interior and sheltered surfaces
- It’s only for professional and industrial use
2. ROOF-GUARD-Insulating-Coating
Roof Guard is a high-build, 100% urethane/acrylic elastomeric roof coating. It’s developed with the latest technology using plastic polymer resins, mildewcides, and weather-resistant pigments for maximum performance. Additionally, the paint contains Hy-Tech’s ThermaCels, insulating microspheres for faster evaporation and moisture repulsion.
During application, ensure the surface is free of elements that may affect adhesion, including dirt, dust, grease, and oils. We recommend Hy-Tech’s House Wash cleaner to remove all elements at a go.
Also, allow the surface to dry after washing, then prime Hy-Tech’s #SR1220 Bond-It primer before painting. When done priming, apply the paint with a roller or paintbrush.
You can also spray the paint if you wish. If so, ensure the sprayer can pump a gallon per minute, use a 0.03-0.04 inch tip size, and remove all sprayer filters.
Pros
- It’s usable on flat or sloped roofs
- Works on all roof types
- Easy to roll or spray-on
Cons
- Only available in a white color
How to Apply Anti-Condensation Paint
Applying condensation-repelling paint is similar to other paints. Here’s how to proceed;
- Surface preparation: Use mold killer to get rid of mold. Any other methods may spread mold spores. Then cover damp spots with a damp seal and remove wallpaper and existing paint. Afterward, wipe the surface clean and allow it to dry before you start painting.
- Mix the paint: Most non-condensation paints require mixing. Only mix by hand to ensure even distribution of the particles.
- Apply the paint: You can apply non-condensation paint by rolling, brushing, or spraying. Two coats are sufficient. Wait 2-4 hours between coats and allow the final coat to dry overnight.
Will Damp-Proof Paint Stop Condensation?
No. Unfortunately, damp-proof paint alone cannot stop condensation. However, it goes a long way in minimizing the problem. Unfortunately, it’s not a fix-it solution that addresses the condensation problems completely. Instead, you must address poor ventilation and other humidity issues to address condensation issues.
What’s the Best Anti-Condensation Spray Paint for Metal?
Tikkurila Grafo Therm is the best anti-condensation spray paint for metal surfaces where dripping water problems occur. It’s thermo-insulating and moisture-repellant, thus significantly reducing condensation. Decicoat T35 and Roof Guard are other good options.
What’s the Best Anti-Condensation Paint for a Metal Sheds?
Grafo Therm is the best non-condensation paint for metal sheds and metal shed roof structures. However, Ronseal Anti-Condensation Paint is another option. Remember to clean the surface before painting. Also, remember to prime the surface.
Alternative Ways to Prevent Moisture Condensation on Metal Roofs
Although condensation-resistant paint is among the best ways to minimize sweaty metal roof issues, a few extra measures can eliminate the problem for good. We recommend the following;
Proper Ventilation
For a mild condensation problem, improving ventilation cures the issue. The easiest way to improve indoor ventilation is to open the doors and windows to boost airflow. Furniture arrangement and overall interior design can also impact airflow.
For instance, more space and less clutter increase airflow. Finally, use fans to direct warm air out of the home.
Control Roof Moisture
We’ve determined that metal roof condensation happens when moist air rises to the attic and condenses when roof temperatures drop below the due point.
So, one of the most effective ways to prevent roof condensation is to prevent moisture from contacting the metal roof. A moisture barrier under the roof does this excellently.
Control Indoor Air Conditions
Another way to minimize roof condensation is by addressing indoor air conditions. Specifically, find ways to eliminate excess moisture from your home.
Two possibilities are air conditioning and dehumidification. Both processes extract excess moisture from indoor air without leaving the air too dry.
Install Roof Insulation
Roof insulation blocks heat transfer via the roof. It’s traditionally used to improve energy efficiency in the home. However, the right roof insulation types block condensation too.
Some of the best roof insulation types for roof condensation control are spray foam insulation, batt insulation, and loose-fill insulation.
Choose the Correct Roof
We specifically recommend anti-condensation sheets. Anti-condensation roofing sheets are specially designed to absorb condensed water and release it back into the atmosphere when outdoor temperatures rise.
The best examples are DripStop roofing sheets (image below), which absorb 1g/m2 of roofing sheet and store the condensate in tiny pockets within the roof membrane.
Paint to Stop Condensation on Metal Roof FAQs
What can I Paint on Metal to Stop Condensation?
Non-condensation paint is the best solution to stop roof condensation issues. These paints are therm-insulating, reflecting warm air away from the metal surface.
In addition, they are moisture-repellent and thus don’t form moisture on the surface. Excellent choices are Tikkurila Grafo Therm and Roof Guard.
What can I Put on a Tin Roof to Prevent Condensation?
Insulation is the best solution to prevent condensation on a tin roof. Specifically, we recommend vinyl-backed fiberglass insulation. It’s easy to apply and lasts many years.
Additionally, it’s low-maintenance. Insulating the roof with fiberglass prevents warm air from coming in contact with the cold roof.
How to Stop Condensation on Steel Roofing Sheets?
The most important step in steel roof condensation control is addressing moisture issues. First, find out what causes the moisture and address the problem.
For instance, dehumidifiers, ceiling fans, and air conditioners can eliminate excess moisture from your home. Besides moisture control, choose the right roof pitch, insulate the roof, and paint the roof with anti-condensation paint.
Summary
Anti-condensation paint is one of the best remedies for metal roof condensation. The thermo-insulating paints are also moisture repellent, thus blocking warm air from contacting the roof while simultaneously blocking moisture formation on metal surfaces. Tikkurila Grafo Therm and Roof Guard are your best options.