Barn conversions offer unique charm and spacious living, but their open-plan layouts and often historic structures can present challenges when it comes to efficient barn conversion heating.
They are definitely not a "formula solution" product and come in very many different shapes and sizes. Mix these size and spatial differences in with a potentially rural location, and although you have the recipe for a unique and beautiful home, you also face the challenge of a rather complex set of parameters for a successful heating system.
In this article, energy expert, David Hilton explores the various heating options available for barn conversions, considering their unique characteristics and offers practical advice for creating a warm and comfortable home.
Factors influencing your barn conversion heating
The two main key performance details for any home are insulation and draft proofing (air tightness). Insulation is the mechanical separation between a cold and warm area which slows down heat transfer. The thicker, and better performing it is, the better.
More is always better but there comes a point where there will inevitably be diminishing returns, meaning there is a level of when you can have too much insulation.
Adding insulation however does become very difficult if you have visible architectural features – which can be common in a barn conversion.
As an example you may have very ornate structural roof trusses that you want to retain. You could wrap the insulation around the truss ends, but ideally the insulation should be placed on top of the sarking. You will ideally need to strip the roof covering (tiles, slate, metal), insulate above the trusses, re-membrane the roof and then replace the cladding.
Dealing with air tightness in a barn conversion
However, a highly-insulated wind tunnel is also not a very efficient space, so it is as important to also exclude as many drafts as possible. Every detail needs to be looked at including all the penetrations through the walls including, doors, windows, drains, pipework and other services.
Historic or listed buildings will have the added difficulty of overcoming any listed details and also maintaining the historical merits of the building. Any repairs should be done respectfully.
Structural repair is often better than replacing the elements with new materials, especially if they are exposed features that are part of the architectural merit of the building. The repair should now be part of the modern history of the building.
However, while traditional barns with timber post-and-beam structures, large open plan areas and high vaulted ceilings, are fantastically beautiful buildings, the nature of the frame is that the timber continually moves as the temperature, humidity and seasons change.
This movement makes air tightness very difficult to maintain and also allows for small gaps to form around the insulation, especially around corners, at the plate levels where the roof joins the wall, or where the wall meets the floor, as well as any penetrations through the walls such as windows, doors, drainage, ventilation or plumbing and electrical services.
A leaky building will have a higher turnover of air and because the air holds heat, the heat loss will be greater and the heating costs higher. As the heat loss increases so does the necessity for higher temperatures in the heat emitters (radiators or underfloor heating), and this can sometimes be a limiting factor when it comes to choosing what technology will deliver the heat to the home.
Choosing the best heat emitters for your barn conversion
A good heat loss calculation, that takes into account the insulation and air tightness, is vital when it comes to choosing the right type of heat emitter for your barn conversion. Heat will also rise up into the vaulted area of the roof which increases the volume that needs to be heated.
The open plan nature of these homes often leaves less wall area for radiators and greater distances between the radiators. To avoid cold spots it is best to plan underfloor heating in the open plan areas, as that way the heat is evenly spread across the floor.
For underfloor heating the harder the flooring surface finish, the better it is for heat transfer. Tiles or concrete are the best, then engineered wood flooring and finally carpets. Carpets are not ideal and any carpet with a tog value of more than 2.5 should be avoided.
Also be aware that underfloor heating is not always on. If you have an efficient home, then the floor heating will turn off when the room reaches the required target temperature.
It is important to balance the floor heating to put in as little heat as possible for the longest period , rather than a hot floor for a short time, but it may also be prudent to use a compromise floor finish such as engineered floor boards in a more efficient home, as the floor will not feel as cool as tiles when the floor is off.
Underfloor heating is very slow to react so should not only be set at the lowest flow temperature, but also should not be turned off, especially if you are running the central heating from a heat pump.
Secondary heat emitters for your barn conversion
As well as your main heating emitters, you can also consider secondary heating appliances such as wood burning stoves. As well as adding ambiance, they also have the ability to heat the space rapidly.
If the barn is air-tight then using a wood burner with a direct air intake (DAI) is best practice so that the air quality in the room is not affected but the combustion process in the burner.
A wood burner with a back boiler can be used, but be very sure that the system is designed with the barn, and occupancy, in mind so that you do not end up with overheating.
Back boilers also cool down the burn so you need to make sure that the burner manages this so you do not have excess products of combustion such as soot and ash.
Shop for heat emitters for your barn conversion
This stove is small but boasts an energy efficiency rating of A making it an option if you're looking for a secondary heating source in your barn conversion
Add a vertical radiator to your barn conversion heating if you're looking for a high temperature emitter
A small bioethanol stove can give a boost to your barn conversion heating if you need an alternative to wood burning stoves
Picking the best heat source for your barn conversion
As your heat emitters only work when connected to a heat source, you'll also need to weigh up what is best for your barn conversion.
Heat pumps do not burn a fuel. Instead they transfer heat into the home in a slow and gentle way. Air source heat pumps move heat from the air outside the property and ground source heat pumps move heat from the ground around the property, but the way they deliver the heat to the home is the same: Low and slow.
For best efficiency, by all means turn the temperature in the area down, say by around 3 degrees, at times when you are not using that space, but do not turn it off. The reheat times of many underfloor heating systems, especially those bedded in a screed or slab, can be long and it is much less efficient to run the heat pump on a reheat as it needs to work harder.
If the barn requires continual high temperatures to keep it warm, then a heat pump might not be the solution. There are heat pumps that can reach higher temperatures but at a compromised efficiency and a lower output.
Biomass boilers on the other hand, naturally produce high temperatures and use a renewable and sustainable fuel source that can potentially be zero carbon. High temperatures are however better suited to radiator based central heating systems.
The radiators can operate at higher flow temperatures delivering high grade heat rapidly to the room. Although high temperature boilers can be used with underfloor heating, the temperature will need to be blended cooler to avoid thermal shock to the floor, as this can cause damage such as screed or tile cracking, as well as discolouration on luxury vinyl type flooring.
Managing heat and humidity in a barn conversion
In vaulted roof areas the warm air that rises into the roof area needs to be de-stratified, either by fitting destratification fans to push the heat back down again, or by designing a whole house mechanical ventilation heat recovery (MVHR) system to do the job for you.
An MVHR system is also a good idea if you have achieved reasonable air-tightness as they keep the home ventilated at the right rate for the occupancy, and also balance the humidity with the external humidity, which helps reduce timber movement and mould growth.
Barns can make great homes. Just be sure to plan the heating strategy and technology solution at a very early stage in the conversion. The heating system must compliment the architecture and materials used in the building, and be carefully planned and controlled.
Sometimes a mix of different solutions is required so early engagement with the installers and design teams is crucial for the best outcome.
Retrofitting central heating systems to already completed barn conversions is disruptive, expensive and does not always deliver on your expectations meaning your barn conversion costs could escalate if you don't get it right from the off.
