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Ducting Insulation for Heat Recovery Ventilation

Duct insulation for HRVs

Home is usually associated with a friendly atmosphere and comfort. Air is an indispensable factor influencing the well-being of residents. Breathing it every day, we almost forget about its existence. We are only reminded of the problem of appropriate air exchange when a foul smell accompanied by dampness appears in the house or, conversely, when the air is dry and we feel tired, have dry eyes or throat.

Indoor air concentrates pollutants such as carbon dioxide, dust, pollen, and water vapour. The excess vapour condenses on the walls, causing dampness and subsequent fungal and mould growth. Ventilation is necessary to ensure proper air exchange.

The decision to install the ventilation system should be made already at the stage of designing the house or planned renovation. Ventilation systems are divided into mechanical, gravity and hybrid – which are a combination of the two previous types.

Mechanical Heat Recovery Ventilation

For more efficient air exchange, a mechanical extract ventilation system and a mechanical balanced ventilation system are used.

Is it worth it? Definitely yes. The ability to control the intensity of ventilation, depending on what we do or how many people are in the room, undoubtedly improves the comfort of inhabitants and possible guests.

The supply air flow rate should balance the amount of air extracted from the rooms. By using mechanical ventilation, these parameters can be controlled. This solution has many advantages.

The air movement is triggered by a fan. The supplied air can be filtered, which reduces the amount of pollen and pollution. The use of airtight windows and doors means that no external noise can reach the rooms. The ventilation system, if designed and installed properly, itself does not cause noise in the house – special duct silencers and sound insulations effectively suppress the noise associated with the movement of the air stream.

The core of the ventilation system, in this case, is the heat recovery unit – a modern device, unlike the old obstructed chimneys, which makes it possible to ensure a comfortable indoor climate

Heat recovery unit for comfort and economy

A heat recovery unit is a device in which the supply air and exhaust air come into contact – without the air streams mixing. Thanks to the heat exchanger inside the heat recovery unit, the air removed from the rooms gives off heat and moisture, which warms and humidifies the outdoor air.

This is particularly useful in winter as the heat exchangers require less energy to heat the air and it has better humidity, despite being dried out by heating systems. Beyond the heating season, mechanical ventilation can be supported by the frequent opening of windows, which allows constant access of fresh air to rooms.

heat recovery units

Check the offer of Heat Recovery Units

This should not be underestimated, as our well-being and health depend on proper ventilation. Although the implementation of mechanical ventilation in the building is associated with certain costs, you can not forget that this is an investment in the health and comfort of users of the premises.

Rising heating and energy prices are forcing those planning to build or renovate a home to look for savings. When looking for ways to reduce building operating costs, proper insulation of ventilation ducts is worth considering. It affects not only the facility’s cost of heating and air-conditioning but also the comfort of the building’s inhabitants and the durability of the entire system.

Thermal insulation consists of two layers: proper thermal insulation and a layer protecting the proper insulation against mechanical damage and environmental impact. Sanitary systems are insulated to reduce heat transfer losses, to protect against water and moisture, and to provide noise insulation.

The greater the difference between the transported medium and the surroundings, the greater the heat loss or gain in the system. Lack of insulation may prevent the rooms from maintaining thermal comfort at the assumed level, and also contribute to an increase in maintenance costs of the facility.

The condensation of water vapour on the surface of the ducts contributes to the formation of corrosion, thus reducing their efficiency and the life of the entire system. Furthermore, excessive moisture inside the ducts creates an ideal environment for bacterial growth and compromises the quality of the incoming air.

What is the purpose of ducting insulation?

  1. Prevention of energy losses can lead to increased energy consumption, lower system efficiency, which in turn can result in higher operating costs of the entire system.
  2. Protection against condensation of moisture on the surface of the ducts. Without vapour barrier ductwork can corrode (which consequently leads to a reduction in the efficiency of the ducts and the life of the entire MVHR system).
  3. Suppression of noise generated by the movement of air in the ventilation duct.

Types of Duct Insulation

There are many types of coverings on the market, both plastic and natural. Popular solutions used to insulate ventilation systems are:

Mineral wool insulation

Mineral wool insulation which is characterized by high thermal resistance and due to their fibrous structure provide good reduction of noise generated by the system. The mineral wool mats are covered with reinforced aluminium foil.

The wool is resistant to degradation caused by micro-organisms and its thermal conductivity coefficient (λ) is between 0.030 and 0.045 W/(m·K). Such coverings are the safest solution in terms of fire, they have the A1 flammability class and meet the condition of fire propagation.

Rubber foam insulation

Rubber coverings characterized by low thermal conductivity coefficient λ (approx. 0.035 W/(m·K)) and closed-cell structure, which ensures excellent thermal insulation properties as a result of reduced heat exchange. Elastomeric rubber foam also has high resistance to water vapor diffusion, which prevents condensation and moisture penetration – the main cause of corrosion on the surface of pipes and ducts.

foam rubber insulation

Rubber mats are available with a self-adhesive layer, which makes the installation process very easy. Due to the flexibility of rubber insulation, it can be adapted to virtually any shape of insulated ducts or fittings. The operating temperature for this type of covering can range from -200°C to even +175°C.

Advantages of foam rubber insulation

  1. The closed-cell structure of the insulation material provides excellent protection against condensation.
  2. Low thermal conductivity coefficient
  3. Resistance to UV radiation
  4. Widely used in heating, air conditioning, refrigeration, plumbing, and ventilation systems.
  5. Simple and quick installation.

Preinsulated ducts and fittings with foam rubber insulation

An alternative solution for on-site insulation of ducts is to choose pre-insulated components from the FOAM System product group, i.e. spiral ducts and fittings (bends, tees, nipple and couplings, reducers) fitted with EPDM seals and foam rubber coverings.

insulated ducting

FOAM SYSTEM Insulated ducting 

Insulation in a form of a mat is available in 4 thicknesses: 9, 13, 19 and 25 mm. Due to the fact that the foam rubber is installed directly on fittings and round ducts, the installation time of the ventilation system is significantly reduced.

The seal used in the system is based on homogeneous EPDM rubber. It is attached to the end of the fitting and firmly fixed around the perimeter through the turned-up edge of the fitting. This ensures that the gasket always remains in place, regardless of the installation conditions.

The FOAM-TAPE rubber foam adhesive tape can be used to join FOAM System elements.

Advantages for FOAM System

  • Fast installation of the insulated ducting,

  • Small insulation thickness [9, 13, 19, 23] with high thermal insulation,
  • Suitable for ventilation systems, including HRV and ducted air conditioning
  • It is used when insulation cannot be added after the ductwork has been assembled.

EPP thermal ducting 

EPP ducting is a system of prefabricated ducts and fittings that exploits the advantages of expanded polypropylene. The most important features of the product are: stiffness of construction, lightness, ease of installation and good thermal insulation.

EPP ducting

EPP ducts are used e.g. as intake and extraction sections in household heat recovery systems. They do not require additional insulation (as the material itself is already an insulator), which significantly reduces installation time.

Each piece can be fastened easily and quickly as no additional fasteners or screws are required. Additionally, foamed polypropylene is easy to cut with hand tools. The system also eliminates the formation of thermal bridges. Due to the low weight of the elements, a suspension system is practically unnecessary. 

Advantages of EPP system

  • Simple installation (no additional mounts, tapes, screws, etc.)
  • Assembly requires little expertise - EPP elements are simply push-fit to connect; ducts can be cut to match our needs using a knife or a saw
  • The system consists of just a few pieces - only 3-4 (a pipe, bend 45o, bend 90o, connector)
  • A lightweight, durable design

Important parameters for insulation of ventilation ducts

When it comes to ventilation and air conditioning systems, an important function of insulation is protection against condensation. It is especially important for duct sections with a cold medium in a warm room and with a warm medium in an unheated room.

To avoid condensation, the temperature of the protected surface must be above the dew point. This is the value of the air temperature to which it must cool in order to reach a saturated state of water vapor.

It is important to remember that water accumulating in the insulation has a negative effect on its properties – as the humidity of the material increases, so does its thermal conductivity coefficient. This results in increased heat or cold loss, i.e. higher energy consumption.

A humid environment also promotes corrosion and the formation of mold and mildew. It is worth making every effort to avoid this, as repairing the damaged system and insulation can be really expensive.

Selection of the right duct insulation thickness

The selection of appropriate covering thickness by the HVAC designer is not without significance. When well-chosen, it ensures a good temperature distribution in the insulation layer.

The thickness is selected according to the principle that the temperature on the surface of the duct should be the same as the ambient temperature. The issue of insulation of building elements is regulated by the provisions set out in the Ordinance of the Minister of Transport, Construction and Maritime Economy of 5 July 2013, amending the ordinance on technical conditions to be met by buildings and their locations. 

Pros and cons of  duct insulation solutions

When choosing a type of insulation we should take into account:

  • the type of system,
  • the impact of external factors,
  • the temperature range of the transported medium,
  • the required fire classification
  • economic considerations – the cost of insulation and possible profit from reducing the costs of operating the facility.

The properties of the insulating material, such as density, vapor-permeability, ecological properties (chemical, biological, dusting potential, toxicity) and mechanical strength will also be important. When choosing insulation, performance properties such as ease of installation are also worth considering.

When a good price is important, mineral wool insulation is the cheapest of the solutions presented. It is also the safest option in terms of fire, as it has the highest flammability class A1. Unfortunately, the installation time is the longest in this case.

Pre-insulated ducts and fittings as well as prefabricated systems that do not require insulation are a much quicker solution. Of course, this also involves a higher price, but the saving on labor is worth considering. Compared to mineral wool, EPP and rubber insulated elements are also characterized by higher resistance to water vapor diffusion.

Would you like to know more? Read other articles on heat recovery ventilation:

  1. How can You install heat recovery unit in the ready-built house?  - the article about decentralized heat recovery systems.
  2. What is an Electrostatic Precipitator and how does it work? - the article about the highest filtration efficiency solutions.
  3. 14 Things You Need to Know about PremAIR - pretty self-explanatory title about the best HRU for clients looking for "premium" solutions. 
  4. Air distribution system for the MVHR - overview of FLX-REKU system: radial, semi-rigid ducting, plenum and distribution boxes, etc.
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