Thursday, 24th December
What is Heat Loss?
There are some basic facts of physics that we cannot overcome. Heat will transfer whenever there is a difference in temperature; and the direction of transfer is always from warmer areas to cooler. However, the rate of this transfer of thermal energy, let’s call it heat loss, can vary and this is the part that we can influence.
Our buildings are essentially enclosures or envelopes. Heat is generated within these envelopes in several ways. We are all familiar with the obvious sources: central heating, radiators, underfloor heating, and open fires. Heat is also generated by appliances, whether computers or washing machines. And by our own body heat.
Adequate heating is an essential element in creating a warm house, however, once heat has been generated it needs to be retained. Many of our clients believe they are losing heat through the building fabric (walls, floors, roofs, and windows) at an unacceptable rate and want to understand where this is occurring and how to remedy it.
Where is heat being lost?
Heat is lost through the following mechanisms: conduction through the building fabric or through air infiltration (cold air in) and exfiltration (warm air out).
The building fabric act as a barrier and slows the rate of heat transfer. However much depends on the quality of the design, the materials, and the workmanship. Some materials are better at resisting the passage of heat than others; and some good materials such as insulation can be rendered ineffective or bypassed completely if they have been installed incorrectly.
Heat is not usually visible, and many parts of the fabric considered important for thermal performance are concealed and inaccessible for inspection. It is not uncommon for homeowners to plan thermal upgrades based on hunches. Thermal imaging surveys offer an alternative to this hit-or-miss approach and can illustrate exactly where heat is being lost.
Heat Loss In Cracks And Defects
Heat can also be lost through cracks, defects, and unsealed service penetrations. Convection currents (both temperature-driven and mass transport) can carry warm air to the outside and often more significantly, draw cold air into the building and cause it to circulate between layers of the construction. The cooling effect of these currents which circulate unseen can be profound; however, they are not often considered by building owners who tend to be more focused on heat leaving their property.
The exception to this is draughts. Homeowners have little difficulty locating draughts. (We have sometimes surveyed houses where there is a steady breeze of cold air coming out of electrical sockets!) Basic draughtproofing can be done cheaply and easily but tends to focus on plugging gaps in the finishes rather than locating the sources of the air infiltration which are usually gaps in the outer leaf of the construction.
How to Reduce Heat Loss in a House
Reducing Heat Loss Causes Big Improvements
- Review your heating control settings. All households are not the same: set the controls so that timings work for the way you live in your house. Ensure that your thermostats are accurately measuring the air temperature. If the thermostat is on a ‘warm’ (or cool external) wall, it may give a false reading. One part of reducing heat loss is not to generate it unnecessarily.
- Fill those draughty gaps! The most common locations for draughts are service penetrations (gas, water, soil, drainage pipes); the junction between the floors and the skirting board; around the bath panel and the shower tray; around the stairs; around kitchen units; through poorly fitting trickle vents; via the loft hatch; through gaps between patio doors and through holes in the ground floor. Remember to research the correct sealant for each location.
- An unused chimney is effectively a huge hole in your roof. Don’t block it up. Have a look at a product like Chimney Balloon which can help reduce the loss of warm air due to the stack effect
- Increase the efficiency of your radiators by reflecting heat away from the wall using radiator foil. We’ve carried out heat loss surveys of traditional buildings where you can ‘see’ where the radiators are from the street by the amount of heat transferring through the walls!
- Hang curtains behind radiators or better still, cut them short so that they hang just above and behind radiators. Do not restrict convection currents
- Lag and insulate the primary pipework for your central heating.
- If you have safe access to your loft, visually check the distribution and thickness of the insulation. Replace any missing or displaced pieces, upgrade loft insulation to 400mm.
Reduce Heat Lost Through Upgrades
- All houses are built using the knowledge and the materials of their times. Things move on. Consider replacing windows and doors with modern thermally efficient products.
- Replace your lights with LED or low energy ones. This should only apply if you have an older property since a percentage of lights in new builds should already be low energy to comply with Building Regulations.
- Consider the thermal properties of your walls if you live in a house with a solid wall construction (for example: a Victorian terrace). Don’t discount wet plaster techniques for solid walls rather than internal wall insulation. See Words of Caution below.
- Retrofit cavity insulation. The technique is highly effective when done well. But again, thought and advice recommended.
Words of Caution
Some warranty providers may restrict or stop your cover if you carry out unapproved alterations. (The NHBC lists installing additional cavity insulation and replacing windows as examples of these types of alterations.) Always check with your Warranty Provider before carrying out alterations.
Fitting insulation is not a complicated business. This may be why so little thought at all is given to it. However, a basic understanding of building physics is needed. Insulation is good, but not all insulation in all situations is good. In fact, quite the reverse.
We strongly recommend that you get advice before installing internal or external wall insulation in traditionally built solid wall properties. To generalise: old properties were constructed to absorb moisture in the winter and release it in the summer. (Modern properties by contrast use materials that stop water from getting into the construction in the first place.) Internal and external wall insulation may under some circumstances lock in moisture and prevent it from being released in the usual seasonal way. This may cause interstitial condensation and could damage the building.
At Thermalume we always look to best practices, so we strongly recommend that you contact registered installers via organisations like FENSA. They can provide you with deeper expertise than a general builder and should offer you an insurance-backed guarantee for new work.
Reduce Heat Lost Through Thermal Imaging Surveys With Thermalume
The advantages of instructing a heat loss survey are obvious: locate the areas in your house which are not performing well thermally, and then use that information to plan for upgrade work intelligently.
Our company motto is: “Heat loss, captured”. And that is a fair description of what we aim to do for our clients, and we’d like to believe that we are part of the due diligence process every homeowner and business should do before and after building works. So, if you are looking for a thermal imaging survey, call today on 07774 292904 or visit our contact page for more details.