How does thermal mass work

The wooden deck, however, does not have relatively large amounts of thermal mass. Although the winter sun shines on it in the afternoon, it does not have thermal mass and does not retain heat. Thus, I had to shovel it. Ideally, within passive solar design, the thermal mass is located inside of the building and is well insulated to keep the structure warm in the winter.

Solar Design. Twitter Facebook RSS. Categories — Sq. Thermal Mass Thermal mass is another vital and complimentary component of passive solar design.

Basic Passive Solar Design. Rock — Sandstone. Rough Aggregate Adobe Plaster. Arranged by final overall standing. Thanks for dropping by. Feel free to share a thought or ask a question. To prevent the potential for overheating thermal mass in summer, it's important to design appropriate eave widths. Good insulation including glazing is essential to maximise the benefits of thermal mass.

It's vital that thermal mass is insulated from outside temperature fluctuations. Without insulation, thermal mass can be a liability — radiating cold and exacerbating damp conditions in winter.

This is particularly important if you only heat for part of the day — the thermal mass will absorb heat from the air until it is the same temperature. If you are using concrete as thermal mass in a floor or wall, you need to be aware that it will not perform at its best until it has dried out.

Drying time will vary depending on humidity and thickness. A mm thick slab can take four months to dry out longer in winter , and thicker slabs will take longer. During that time it is particularly important to ventilate the house regularly to avoid the build-up of internal moisture. Some homes have thermal mass that isn't being used. Any concrete slab in a north-facing room can absorb and store heat, so long as it's uncovered and insulated.

It may be worthwhile ripping up a carpet and putting ceramic tiles down to reduce some overheating in summer and capture some free solar gains in winter. Download a comprehensive guide to designing more comfortable houses from the Cement and Concrete Association of New Zealand's website.

You can book them for free personal advice on your home design. Skip to main content. Visit building. Home Smart Guides Tools and resources Case studies. Thermal mass keeping your home comfortable These materials are heavy and dense, and therefore high in what is technically called thermal mass.

Thermal mass materials Probably the simplest form of thermal mass is a concrete slab floor. The ideal material is: dense and heavy, so it can absorb and store significant amounts of heat lighter materials, such as wood, absorb less heat a reasonably good heat conductor heat has to be able to flow in and out has a dark surface, a textured surface or both helping it absorb and re-radiate heat. Where you should put thermal mass Thermal mass should be placed where it will best be able to absorb heat in the colder months and be shaded in the warmer months.

You can also put thermal mass near a woodburner, heater or another source of radiant heat. Where you shouldn't put thermal mass Thermal mass can be a liability if used incorrectly, so it should be kept away from: cold, draughty areas such as entryways or unheated hallways rooms that face south or don't get much winter sun areas with poor insulation.

Thermal mass in floors In most climate conditions a concrete slab, insulated underneath and around the edge, where it is in direct contact with the ground, is the most effective way to increase thermal mass. Thermal mass in walls Brick, concrete, concrete block including insulated and aerated types and rammed earth can be used for internal or external walls if they catch the sun or are close to a radiant heat source.

Other options Other options include: feature brick or stone walls Trombe walls. A trombe wall is a north-facing heavy wall made of concrete or some other thermal mass material, located behind a layer of glass. The wall's exterior is dark-coloured to attract the sun's heat.

The heat takes several hours to travel through the wall before it is released into the home's living areas. Properly designed, it should start to release heat in the early evening as the temperature starts to fall. They can be used to maximise heat collection when views and glazing are oriented to the south or when site orientation is not ideal. How much thermal mass do you need?

Area The area of exposed thermal mass should be balanced against the area of glazing. Thickness Concrete slab floors should be —mm thick for the best performance, while thermal mass walls should be —mm thick. Because thermal mass distinguishes itself as a tool for dampening of temperature amplitudes, it works best where excessive heat builds up and requires absorption and much later disposal.

For example, where the excessive heat generated by solar-gain is absorbed by the building fabric during daylight hours or where in a school environment excess heat is generated by students and absorbed for emission into a cooler night-time space. Where buildings normally experience these kind of temperature differences, the use of thermal mass can make plenty of sense - but where there is little normal amplitude variation typical of a Passivhaus dwelling, the case for the special consideration and use of thermal mass starts to become more marginal and complicated.

In houses, as the climate becomes warmer, the more noticeable heat load will increasingly come from solar gain during summer months. In a Passivhaus dwelling the gain will present a significant challenge to the design of the house.

Arguably one way of dealing with the heat will be to use thermal mass to absorb the excess - but to avoid overheating, it will be usually necessary to flush away the heat during the night. A good deal of opening of windows will likely be needed - and then will be only successful if the night-time temperature is sufficiently below that of the day-time peak. Another alternative would of course be to prevent solar gain through control of how much sun is transmitted into the building.

Either way, the design and use of thermal mass will be carefully integrated into the context of both other controls and the pattern of use of the particular building. Thermal mass will be dependent on context.

Particular effort is being directed at materials based on the change of paraffin from solid to liquid phases. Products include aluminium clad panels containing paraffin see Dupont Energain above and encapsulated paraffin capsules mixed with plaster. GreenSpec accepts no responsibility or liability for any damages or costs of any type arising out of or in any way connected with your use of this web site.

Data and information is provided for information purposes only, and is not intended for trading purposes. Neither GreenSpec nor any of its partners shall be liable for any errors in the content, or for any actions taken in reliance thereon. Thermal admittance, or 'Y-value,' or Heat transfer coefficient Thermal admittance quantifies a material's ability to absorb and release heat from a space as the indoor temperature changes through a period of time.

Admittance values for typical external wall elements based on a 24 hr cycle External wall Internal finish Admittance value Timber frame brick outer leaf Plasterboard 1. A material of 'high' thermal mass has a high specific heat capacity. A high density material maximises the overall weight and is an aspect of 'high' thermal mass. Thermal conductivity Thermal conductivity measures the ease with which heat can travel through a material.

For 'high' thermal mass, thermal conductivity usually needs to be moderate so that the absorption and release of heat synchronises with the building's heating and cooling cycle. K The effectiveness of some common materials: Material Specific heat capacity Thermal conductivity Density Effectiveness water 0.