Poweranne's Thermal Mass
Sustainability was at the core of the design. It was built in conjunction with a 200 per cent extension of an existing solar power system, which now has sufficient generating capacity to cover 90 per cent of the clients’ residential and winemaking needs. In addition to passive solar design techniques – exposed thermal mass, heavily insulated walls and roof, operable windows for cross ventilation, and eaves over all windows – the design team sought to further their clients’ commitment to sustainable design by researching the idea of ecological custodianship. “We folded our insights back into our specification processes, making predominant use of plantation and native regrowth timber, and detailing our materials to heighten their durability and natural character,” says Mihaly. “We also invested ourselves in off-site manufacturing processes, in particular for the external window shutters. Entirely customised, we first designed these with millimetre accuracy on the computer, then prototyped them in close conjunction with the builder, steel fabricator, electrician and CNC router to perfect them. This was a first for us: never before had we been so closely involved in the manufacture o...
Solar Tube Location: Dobling, Austria Size: 3,315 square feet (308 square meters) Natural light dominates this glass house, reducing the need for daytime lighting and allowing ample opportunity for solar heating. It also features a Trombe wall, a southward-facing wall that receives direct sun (in the Southern Hemisphere, Trombe walls face northward). The wall absorbs heat in warm temperatures and has vents at the top and bottom that can be adjusted to cycle air and release heat during warm weather. The view pictured, from the stairs looking toward the library, shows the second floor of the home and the top of the Trombe wall, where the vents can be opened to increase airflow
One of the many new standards that are elevating green practices, Passivhaus originated in Germany; it focuses on a structure’s envelope and interior health. This home, just north of Paris, is the second-most-recognized passive house in France. It has no heating system, instead relying on home orientation, sturdy prefabricated wood panels, bamboo siding and an industrious design to stay warm. The large windows of the bedrooms face south to capture sunlight, while the north side, with fewer windows, prevents heat from escaping.
Rammed earth is such an amazing wall finish. Not only does it display the colour and characteristics of the natural environment, but it provides a solidity that only concrete can mirror. In this beautiful home, CCS Architecture has combined the use of rammed earth with timber. The timber wall has similar toning and horizontal banding to the rammed earth wall.
Thermal mass Materials with thermal mass are dense and can store heat within and include concrete, masonry, stone and rammed earth. The capturing of heat in thermal mass is best suited to regions with sunny days and cold nights. The thermal mass acts as a heat bank, storing the warmth from the sun during the day. In the evening, as the temperature drops, the heat is gradually released maintaining a comfortable internal temperature and reducing the need for mechanical heating. This house, designed by Swell Homes, utilises reverse brick veneer (RBV) and an exposed concrete slab for thermal mass. RBV is where the inside wall is brick and the outside is clad in another material such as fibre cement, timber or render. RBV is a very effective, thermally efficient wall system when coupled with appropriate insulation and external cladding.
Passive Natural heating The majority of Australian houses fall within the climate that benefits from passive solar heating. This is where you can capture the warm winter rays inside your home, naturally heating it. This can be achieved as the sun is lower in the sky over winter, allowing the sun’s rays to penetrate deeply into your home, especially on the north-facing facade, as is the case in this abode. The dwelling has extensive north-facing windows in the lounge and living room taking full advantage of the sun’s heat.
The warmth of concrete Although we traditionally think of concrete as a ‘cold’ material, if used with access to direct sunlight, it can act as an effective thermal mass, meaning it absorbs heat, stores it and then slowly releases it over the rest of the day and into the night in a way that timber or carpet can’t. This is why many solar passive houses have concrete floors. Of course, concrete can ‘look’ cold, but it can easily be warmed up by teaming it with warmer-looking materials. In the kitchen above the concrete creates a lovely contrast to the warmth of the timber.
While straw is a relatively good insulation material, beware that sometimes literature in favor of this technique tends to overestimate the quality of an average bale. Each and every bale should be inspected for consistency and integrity, and should be well dried out. That being said, a construction site full of dry straw can be quite a fire hazard. Particular attention needs to be paid to storage and access during the construction phase.
Gray also wanted the home to function for his family for many years to come. So he employed many universal design principles, many of which center around the use of a wheelchair in the home. A ramp leads to the front door, for example; all the hallways are 5 feet wide, and the doorways are 3 feet wide. All the outlets are more than 16 inches off the ground, and none of the showers have thresholds.
In the wet climate, concrete walls seemed like a practical choice. “Bugs can’t eat it; there’s no mold issues,” Gray says. Plus, it’s durable and easy to insulate. The walls are a sandwich construction that consists of 2 inches of concrete, then 7 inches of Styrofoam, followed by a 5-inch structural layer of concrete with rebar. The concrete panels were cast onsite and lifted into place by a crane. The exterior shows the beautiful wood-grain impressions left by the formwork from casting the concrete.
The cost of heating was a driving factor. Gray didn’t want high energy bills, so he spent time crunching numbers before making a choice. “If I doubled my wall insulation by spending an extra $4,000, then it saved me well over $200 per month on average for my heating bill. It was a no-brainer,” he says. Once he put solar panels on the roof, his heating bill dropped to nothing, he says. The solar system cost about $40,000. “For $30,000 to $35,000, I could have gotten geothermal, but I’d still have an energy bill. For $40,000 worth of solar, I won’t,” he says. The home is set up for rainwater collection too, but Gray didn’t want to spend the $7,000 for tanks just yet. “At some point, I had to stop spending money,” he says. For another $7,000 he could also purchase a battery system that would store energy from the solar panels to take the house completely off the grid.
In Situ ArchitectureSave to IdeabookEmail Photo The house uses a heat recovery ventilator, common in passive design, for fresh, filtered air and enhanced climate control. “The ventilator captures the heat from the exhausted air, and uses that heat to warm the fresh outside air to room temperature, all while using very little energy,” says Stern. The ventilator in this house is stored in a utility room.
One way the Passive House standard verifies the absence of air leakages is with the Blower Door Test, in which the entire house is closed up and air is pumped inside. A gauge, shown here, then measures the air-flow rate relative to the volume of the house. Tests like this, along with energy simulations, measure whether a home is built to the Passive House standard.
Blown-in insulation is a good choice for attics. Fiberglass comes in a loose form and can be blown in, but cellulose is the most ecofriendly choice for blown-in insulation. Cellulose is made from recycled newsprint and treated with an additive to make it fire resistant. Make sure recessed lights are rated to touch the insulation and that no knob and tube wiring is present.
The rammed-earth wall was built in stages, about 1½ feet at a time. Formwork shutters were bolted onto a larger frame and filled with a mixture of dirt, 8 percent cement and a small amount of water. The mixture was tamped down with handheld rammers to compact it, forming the first 1½ feet of the wall vertically. When the shutters were full, another set was attached to the frame, and the process was continued upward until the wall was complete. Sealed with clear sealant for waterproofing
Sustainability. The same goes for the ‘sustainability’ principle of thermal mass – there can be high ‘embodied energy’ in building with thermal mass, such as concrete, in that a great deal of energy goes into its manufacture. But this can often be balanced against the potential future energy savings.
Good glazing. Thermal mass needs to be used in conjunction with other passive solar design techniques, such as orientation, glazing, and insulation. Large areas of glazing on the north side of the home allow the sun to hit the thermal mass so that it can absorb heat. The amount of glazing and where it’s located depends on the regional climate.
Day and night. Thermal mass is particularly good for climates with a high ‘diurnal’ difference, which simply means a big range between day and night temperatures. This is the case for many climates in Australia, including dry desert climates, but less so for tropical climates (though designed effectively, thermal mass can still be used for tropical climates). Use of thermal mass will help to regulate these environments and keep the temperatures constant.
Liquid mass. Water can even be used as thermal mass. In this home, a line of fibreglass water tubes are filled with water and clad with copper at the top to allow for maintenance. At night, LED lighting illuminates the tube for a special effect. It’s an interesting concept though many would probably prefer to opt for a rammed earth, brick or precast concrete!
Thermal Mass Materials matter. ‘Thermal mass’ describes a material that has the ability to absorb and store heat. Materials with high thermal mass take a long time to heat up and to cool down. So in cool weather, thermal mass can absorb heat, store it and slowly emit it at night, while in warm weather, thermal mass can help to maintain a building’s cool when used correctly. Brick, for example, has thermal mass, but timber floors and brick veneer do not.
EXPERT TIPS: Many strawbale houses are built by owner builders with help from friends and the community, attracting as they do interest and enthusiasm. However, as with any construction, it helps to get the experts in for crucial elements of the build. “I have found straw requires a specialist contractor to install it or at least provide advice and equipment at critical stages of construction,” says Brennan. “You can have standard construction below the straw to provide normal termite and damp proofing, but from the floor level up a specialist contractor can advise on the bottom/top frame, laying of bales and tensioning. “The specialists all seem to be happy to work side by side with the owners, as most people who want to use straw like to be involved in the construction. Straw is also an alternative construction method in the Building Code of Australia, so an engineer or specialist consultant is required for council approval.”
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