More Views. Add to Basket. Description Details Common errors in details such as poorly proportioned doors and windows not only hurt the visual appeal of traditional buildings, but also undermine its structure and function This handy, practical resource offers an illustrated, drill-down approach to the rules-of-thumb for details.
A high mass building needs to gain or lose a large amount of energy to change its internal temperature, whereas a lightweight building requires only a small energy gain or loss to change the air temperature. This is an important factor to consider when choosing construction systems and assessing climate change adaptation. Allow thermal mass to absorb heat during the day from direct sunlight or from radiant heaters.
It re-radiates this warmth back into the home throughout the night. During the day protect the thermal mass from excess summer sun with shading and insulation if required. Thermal mass is most appropriate in climates with a large diurnal temperature range.
Exceptions to the rule occur in more extreme climates. In cool or cold climates where supplementary heating is often used, houses benefit from high mass construction regardless of diurnal range e. Hobart 8. Cairns 8. Glass to mass ratios compare the area of solar exposed, passively shaded, north-facing glazing to the area of exposed, insulated internal mass walls and floor , to avoid overheating passive solar houses.
The graph below shows recommended glass to mass ratios for Australian capital cities.
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NOTE: These rules apply only to predominantly north glazed passive designs with guaranteed solar access. Modelling with energy rating software is the only reliable way to validate them. In rooms with good access to winter sun it is useful to connect the thermal mass to the earth. The most common example is slab-on-ground construction. Less common examples are brick or earthen floors, earth-covered housing or green roofs see Construction systems.
A slab-on-ground is preferable to a suspended slab in most climates because it has greater thermal mass due to direct contact with the ground. This is known as earth coupling. Deeper, more stable ground temperatures rise beneath the house because its insulating properties prevent heat loss. It also provides a cool surface for occupants to radiate heat to or conduct to, with bare feet. This increases both psychological and physiological comfort. In winter, the slab maintains thermal comfort at a much higher temperature with no heat input.
The addition of passive solar or mechanical heating is then more effective due to the lower temperature increase required to achieve comfortable temperatures. Use surfaces such as quarry tiles or simply polish the concrete slab. Do not cover areas of the slab exposed to winter sun with carpet, cork, wood or other insulating materials: use rugs instead. The vertical edges of a slab-on-ground are required to be insulated in Zone 8 cold climate or when in-slab heating or cooling is installed within the slab see Clause 3.
Insulate slab edges in cold climates or where in-slab heating or cooling is installed within the slab.
The whole slab must be insulated from earth contact in cold climates and regions with low earth temperatures at 3m depth e. Tasmania or hot, humid climates with high earth temperatures e. Consider termite proofing when designing slab edge insulation. Take care to ensure that the type of termite management system selected is compatible with the slab edge insulation.
Masonry walls also provide good thermal mass. Recycled materials can be used e. Avoid finishing masonry walls with plasterboard as this insulates the thermal mass from the interior and significantly reduces its capacity to absorb and re-release heat. Reverse brick veneer is an example of good thermal mass practice for external walls because the mass is on the inside and externally insulated. In traditional brick veneer, the mass of the brick makes no contribution to thermal storage because it is insulated from the inside and not the outside.
To determine the best location for thermal mass you need to know if your greatest energy consumption is the result of summer cooling or winter heating. Heating : Locate thermal mass in areas that receive direct sunlight or radiant heat from heaters. Heating and cooling : Locate thermal mass inside the building on the ground floor for ideal summer and winter efficiency. The floor is usually the most economical place to locate heavy materials, and earth coupling gives additional thermal stabilisation in both summer and winter in these climates.
Locate thermal mass in north-facing rooms with good solar access, exposure to cooling night breezes in summer, and additional sources of heating or cooling heaters or evaporative coolers. Locate additional thermal mass near the centre of the building, particularly if a heater or cooler is positioned there. Feature brick walls, slabs, water features and large earth or water-filled pots can be used. Cooling : Protect thermal mass from summer sun with shading and insulation if required.
Allow cool night breezes and air currents to pass over the thermal mass, drawing out all the stored energy. Avoid use in rooms and buildings with poor insulation from external temperature extremes and rooms with minimal exposure to winter sun or cooling summer breezes. Thermal mass can increase energy use when used in rooms where auxiliary heating or cooling is the only means of adjusting the temperature because it slows the response times. Careful design is required if locating thermal mass on the upper levels of multi-storey housing in all but cold climates, especially if these are bedroom areas.
Natural convection creates higher upstairs room temperatures and upper level thermal mass absorbs this energy. On hot nights upper level thermal mass can be slow to cool, causing discomfort. The reverse is true in winter. Climatic consideration is critical in the effective use of thermal mass. Think about the impact of predicted changes in climate due to global warming. This is a particularly important issue in tropical climates where temperatures are already close to the upper comfort level. For the main features of these climates see Design for climate.
Traditional Construction Patterns: Design and Detail Rules-Of-Thumb by Stephen A. Mouzon
Use of high mass construction is generally not recommended in hot humid climates due to their limited diurnal range. Passive cooling in this climate is usually more effective in low mass buildings. Thermal comfort during sleeping hours is a primary design consideration in tropical climates. Lightweight construction responds quickly to cooling breezes.
High mass can completely negate these benefits by slowly re-releasing heat absorbed during the day.
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Maintaining thermal comfort in these benign climates is relatively easy. Well-designed houses should require little if any supplementary heating or cooling. The predominant requirement for cooling in these climates is often suited to lightweight, low mass construction. High mass construction is also appropriate but requires sound passive design to avoid overheating in summer.
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In multi-level design, high mass construction should ideally be used on lower levels to stabilise temperatures. Low mass on the upper levels ensures that as hot air rises through convective ventilation it is not stored in the upper level as it leaves the building. This is particularly important if sleeping spaces are located on upper levels. Ground and first floor spaces should be capable of zoning closing off to prevent temperature stratification in winter.
Winter heating is the main need in these climates although some summer cooling is generally required. Ceiling fans usually provide adequate cooling in these low humidity climates. High mass construction combined with sound passive solar design and high level insulation is an ideal solution.
Good solar access is required in winter to heat the thermal mass. Insulate slab edges and the underside of suspended slabs in colder climates. It is advisable to insulate the underside of a slab-on-ground in extremely cold climates see Insulation installation. Buildings that receive little or no passive solar gains can still benefit from high mass construction if they are well insulated. However, they respond slowly to heating input and are best suited to homes with high occupation rates. Auxiliary heating of thermal mass is ideally achieved with efficient or renewable energy sources such as solar, gas or geothermal powered hydronic systems.
In-slab electric resistance systems are slow responding and cause higher greenhouse gas emissions see Heating and cooling. Use a solar conservatory in association with thermal mass to increase heat gains. A solar conservatory is a glazed north-facing room that can be closed off from the dwelling at night.
Shade the conservatory in summer and provide high level ventilation to minimise overheating. Reflective internal blinds also reduce winter heat loss. Both winter heating and summer cooling are very important in these climates.
High mass construction combined with sound passive heating and cooling principles is the most effective and economical means of maintaining thermal comfort. Diurnal ranges are generally quite significant and can be extreme.
High mass construction with high insulation levels is ideal in these conditions see Insulation. Where supplementary heating or cooling is required, locate thermal mass where it is exposed to radiation from heaters or cool air streams from evaporative coolers. With the low humidity in these climates, ceiling fans generally provide adequate cooling comfort in a well-designed home. Underground or earth covered homes give protection from solar radiation and provide additional thermal mass through earth coupling to stabilise internal air temperatures. When renovating, remove carpet or insulating coverings from concrete slabs that are exposed to winter sun.
The slab surface can be tiled or cut and polished to give an attractive and practical finish see Concrete slab floors. Thermal mass can also be increased by adding brick or stone veneers to existing interior walls. In some cases it may be necessary to reduce the amount of thermal mass exposed to the building interior where insufficient passive heating or cooling is available to maintain comfort. In such cases, additional auxiliary heating or cooling is required. To isolate existing mass, line the interior wall surface with sheet insulation materials and plasterboard.
If planning an addition, engage a thermal performance assessor to model your whole home to identify strengths and weaknesses in relation to windows orientation and size and appropriate levels of thermal mass. This model identifies problem areas that might be able to be overcome by adding or deleting new rooms. For heating dominated climates, add thermal mass where winter solar access is already available, such as those buildings with good northerly access. This may be achieved by exposing existing concrete as above or adding thermal mass to walls.
Where the existing floor is slab-on-ground, non-loadbearing walls can be built directly on the concrete slab, after engineering checks are carried out. If the existing building has a raised timber floor it is often practical to combine reverse brick veneer with a retrofitted suspended concrete slab. The underside should be insulated and well ventilated if not earth coupled.
For cooling dominated climates, thermal mass must be protected from summer sun and exposed to cooling night breezes. Add shading to protect thermal mass from summer sun both internally and externally, particularly outside windows and in uninsulated double brick walls. Introduce thermal mass within lightweight structures by using isolated masonry walls, water filled containers, phase change materials PCMs or lightweight steel-framed concrete floors. Internal or enclosed water features such as pools can also provide thermal mass but require good ventilation and must be capable of being isolated, as evaporation can absorb heat in winter and create condensation problems year round.
Air enters this building across the pool thermal mass through a semi-enclosed courtyard. It is evaporatively cooled before entering the building. Roof-mounted solar heating of pools is relatively inexpensive and can be used in conjunction with hydronic heating systems or water storage containers to heat thermal mass in winter or in reverse supply radiant cooling to night skies in summer.
This method can resolve situations where direct solar access for passive heating is unachievable or where conventional thermal mass is inappropriate e. High density : The more dense the material i. For example, concrete has high thermal mass, aerated concrete AAC blocks have moderate to low thermal mass, and insulation has almost none. If conductivity is too low, passive heating can escape from your home before being absorbed. If conductivity is too high e.
For example, rubber has high density but is a poor conductor of heat. Brick and concrete have high density and are reasonably good conductors. Appropriate thermal lag : The rate at which heat is absorbed and re-released by uninsulated material is referred to as thermal lag.
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Lag is dependent on conductivity, thickness, insulation levels and temperature differences either side of the wall. Consideration of lag times is important when designing thermal mass, especially with thick uninsulated external wall systems like rammed earth, mud brick or rock. In moderate climates, a 24 hour lag cycle is ideal. The table indicates lag times for common materials. Rammed earth, rock and mud brick have a low insulation value and rely on thicknesses of mm or more to increase thermal lag. Low reflectivity : Dark, matt or textured surfaces absorb and re-radiate more energy than light, smooth, reflective surfaces if there is considerable thermal mass in the walls, a more reflective floor will distribute heat to the walls.
The amount of useful thermal storage is calculated by multiplying the VHC by the total accessible volume of the material, i. Water has the highest VHC of any common material. The table tells us that it takes KJ of energy to raise the temperature of one cubic metre of water by one degree C, whereas it takes only KJ to raise the temperature of an equal volume of concrete by the same amount.
In other words, water has around twice the heat storage capacity of concrete. The VHC of rock usually ranges between brick and concrete depending on density. The VHC of any material is reduced or even eliminated if the material is covered with linings such as carpets, plasterboard, timber.