17th Nov 2023 -

Condensation on pipes can cause various problems, from cosmetic damage to mould growth. Proper insulation for water pipes is key to preventing these issues by controlling surface temperatures and moisture.

For this feature, we provide you with a comprehensive guide to understanding pipe condensation and choosing suitable insulation materials and installation methods to combat it effectively.

We examine how condensation forms on pipes and why it causes so many problems, as well as outline the main types of pipe insulation. Plus, we provide tips on selecting the right thickness and configuring insulation to prevent issues at joints, elbows and hangers.

By the end, you will have the knowledge to confidently select, install and maintain water pipe insulation that prevents condensation. 

What is the issue with condensation on pipes?

The moisture from condensation can create cosmetic damage. Droplets run down and stain or corrode pipes and surrounding surfaces. As a result, it leads to an unsightly appearance around pipes. Also, the wet surfaces enable mould growth. Not only does it look bad, but mould growth can lead to potential health hazards. 

In cold conditions, condensation can freeze into ice that obstructs water flow or even causes burst pipes. Over time, the moisture also corrodes metal pipes, weakening them structurally. Beyond pipe integrity, condensation also leads to energy loss. This is because uninsulated cool water pipes waste cooled air into the environment through heat transfer. 

In addition, excess condensation can pool and then drip. It potentially results in damage below pipes or promotes leaks at joints. The primary issue with pipe condensation is that it provides a continuously wet environment for mould, corrosion and leaks to occur.

Properly insulated pipes - also known as pipe lagging - maintain their surface temperature to prevent condensation from forming in the first place.

Different types of pipe insulation

When choosing the right insulation for pipes, there are several common options to consider. Each type of insulation has its advantages and disadvantages regarding performance factors like temperature resistance, moisture absorption and ease of installation.

Below, we provide an overview of the main materials to lag a pipe.

  • Mineral wool: Mineral wool contains spun rock or slag fibres. It is non-combustible, moisture resistant, and often used for high-temperature applications. However, it can be rigid and difficult to install around complex piping.
  • Fibreglass: Fibreglass insulation contains spun glass fibres bonded with a thermosetting resin. It provides effective insulation and is one of the most affordable options. However, it can be irritating to work with.
  • Elastomeric foam: This type of insulation is made from synthetic rubber materials to create rubber pipe insulation. It is flexible, moisture resistant, and provides a smooth finish. But this pipe-lagging wrap can be punctured easily.
  • Calcium silicate: Calcium silicate insulation contains hydrous calcium silicate under pressure. It is high-temperature resistant, light and fireproof. But it can be fragile and absorb moisture.
  • Polyethylene foam: Polyethylene foam insulation, or foam pipe insulation, includes closed-cell foam that resists moisture absorption. Available in tube form, it is flexible and easy to install. However, it is combustible and not ideal for hot temperatures.

Can you use the same insulation for indoor and outdoor areas?

Generally, it is not recommended to use the same pipe insulation materials for indoor and outdoor applications. This is because different conditions require different insulation properties.

Despite this, depending on your project, some insulation materials may suffice for both interior and exterior settings. Here are the insulation materials to think about.

1. Fibreglass: It is effective for controlling condensation on indoor cold water pipes. Also, an additional vapour barrier is not always required.1. Calcium silicate: Can withstand high temperatures and weather extremes outdoors while preventing condensation through thermal stability.
2. Polyethylene foam: Provides good moisture resistance. The flexible foam can wrap closely around pipe contours.2. Elastomeric foam: Rubber foam insulation is commonly used to insulate outdoor pipes prone to condensation.
3. Elastomeric foam: Made from flexible and synthetic rubber, this insulation type suits indoor pipes susceptible to condensation issues.3. Mineral wool: Withstands outdoor temperature swings while upholding waterproof qualities. It is effective at preventing exterior pipe condensation.
4. Mineral wool: It is inherently fire-resistant and commonly used for condensation control on indoor steam or hot water pipe systems.4. Polyisocyanurate: With a high R-value and complete waterproofness, this type (also known as PIR) insulates outdoor pipes against condensation.
5. Insulating cement: Applied like paint, insulating cement prevents condensation on small components like valves and fittings.5. Cellular glass: It is completely waterproof and prevents condensation even when constantly exposed to rain and humidity outdoors.

How to install pipe insulation: A step-by-step guide

Proper installation of pipe insulation is key to preventing condensation issues. Follow this step-by-step guide to control surface temperatures and prevent problematic condensation from forming. 

1. Assess your pipes

You should begin by conducting a thorough inspection of your piping system. Identify areas where condensation is likely, such as sections with significant temperature differences. Consider both interior and exterior pipe insulation in your assessment.

2. Gather tools and materials

Once you have assessed your pipes, gather the necessary materials and tools for the job.

InsulationMeasuring tape
Vapour barrierUtility knife
Sandpaper or wire brushInsulation sleeves (optional)
Fasteners or adhesiveCustom fittings (optional)
Safety gloves and gogglesAdhesive tape or sealant

Ensure the insulation material you choose is appropriate for the specific conditions your pipes will face. You should take into account factors like temperature, moisture and potential physical impact.

3. Measure and calculate

Accurate measurements are crucial. Use a measuring tape to determine the diameter and length of the pipes you intend to insulate. Calculate how thick the insulation should be based on these measurements and the thermal conductivity of the chosen material.

4. Select insulation material

Consider the properties of different insulation materials. Fibreglass is a common choice for its thermal resistance, while foam insulation provides excellent moisture resistance. Select the material that best suits your needs. 

5. Prepare the surface

Clean the pipe surface thoroughly before applying insulation. You can use a wire brush or sandpaper to remove any dirt or rust. A clean surface ensures proper adhesion and helps the insulation material adhere securely.

6. Apply adhesive or fasteners

Depending on the type of insulation, apply the adhesive evenly along the length of the pipe or use fasteners to secure the insulation material. Be sure to follow the manufacturer's recommendations for the specific adhesive or fastening method.

7. Install insulation

Start to wrap the insulation material around the pipe and create a tight fit. For straight pipes, consider using pre-formed insulation sleeves for a more precise and secure installation. The insulation should be pulled snugly to avoid gaps or sagging.

8. Seal joints and gaps

Inspect the insulation for any joints or gaps between sections. Use a compatible sealant or adhesive tape to seal these areas. Creating a continuous and airtight barrier is crucial to prevent condensation.

9. Insulate fittings and valves

Pay special attention to fittings, valves and other irregularities in the pipe layout. Cut the insulation material to fit around these components, ensuring complete coverage. You may need to use additional insulation to make sure all components are covered.

10. Consider vapour barriers

In environments with high humidity, consider adding a vapour barrier over the insulation. This additional layer helps prevent moisture from penetrating the insulation, leading to condensation issues.

11. Secure the insulation

Be sure to use additional fasteners or specialised tape to secure the insulation in place. Pay attention to areas where the insulation may be prone to sagging, such as vertical sections, and ensure a tight and secure fit.

Should you maintain pipe insulation to prevent condensation?

Yes, it is important to properly maintain pipe insulation to prevent condensation issues. Depending on the insulation type, we recommend inspections between 2-4 times per year. More frequent inspections may be needed in high-moisture areas. Below are some general guidelines to take into account. 

  • Inspect insulation regularly: This allows you to identify any damage, gaps, or compromised vapour barriers early before moisture can penetrate and cause condensation issues.
  • Re-tape seals annually: Tape and seals degrade over time. Re-taping maintains the integrity of the vapour barrier that prevents moisture ingress leading to condensation.
  • Check pipe hangers: Loose hangers allow insulation to become compressed or create gaps, reducing its effectiveness against condensation.
  • Clean debris: Debris holds moisture against the insulation, promoting condensation and mould growth. Keeping insulation clean and dry prevents this.
  • Repair leaks immediately: Leaks saturate insulation with moisture, compromising its insulating ability. Quick leak repairs prevent significant condensation damage.
  • Preventative re-insulation: Periodic full re-insulation maintains optimal condensation prevention. For example, with copper heating pipes, you should re-insulate every 8-12 years for effective copper pipe insulation. 
  • Replace damaged insulation: Holes, tears or missing sections create gaps that allow moisture access and temperature changes, resulting in condensation.

6 top tips for boiler pipe insulation

Insulating boiler pipes provides several important benefits. The insulation prevents wasted heat loss from the hot boiler pipes and improves overall energy efficiency. Plus, insulation controls surface temperatures, avoiding problematic condensation that can corrode pipes over time.

Freezing risks are also reduced in boiler hot water distribution lines. For a successful installation, make sure to action the below 6 top tips. 

1. Pick the right insulation

Use high-temperature-rated condensate pipe insulation like mineral wool near the boiler due to extreme heat. This can withstand temperatures over 1000°F (approximately 537.7°C). 

2. Cover all bases

Insulate all boiler pipes including hot water supply and boiler condensate pipe, not just the main boiler piping. Insulating all associated boiler piping prevents systemic heat loss and creates an effective heating pipe insulation system. 

3. Insulate fittings and valves

Like all other areas, be sure to insulate valves and fittings that are prone to heat loss due to complex shapes. For this, it is advised to use moulded insulation covers or multiple pieces to fully cover fittings, such as an outdoor tap. 

4. Use appropriate fixings

Be sure to use insulation hangers to support insulated pipes properly without compressing the insulation. This maintains the intended insulation thickness and performance.

5. Securely fit the insulation

Ensure a tight fit of insulation around pipes with no gaps that allow heat loss. Use proper adhesive and sealant to prevent air gaps in insulation.

6. Utilise metal jacketing

Install metal jacket covers on boiler pipe insulation for protection and aesthetics. Metal jacketing resists damage and provides a clean, finished look.

Where to find the best pipe insulation materials

Choose from industry-leading brands of fibreglass, foam, wool and other pipe insulation materials. Our products are designed to prevent condensation, corrosion, freezing and heat loss in pipes ranging from low to extremely high-temperature applications. Plus, we supply all necessary accessories like vapour barrier tape, metal jacketing and adhesive.

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