Tag Archives: Energy Savings

Thermal Comfort

Nowadays, you can see sustainable buildings and green design solutions everywhere. But what does it actually mean?  Is a so called sustainable home automatically environmentally friendly?  How to distinguish between real sustainable design and one that claims to be?

 

What IsThermal Comfort And Why Is It So Important For The Well-Being?

What is thermal comfort?

Human thermal comfort describes the state of mind that expresses satisfaction with the surrounding environment and refers to several conditions in which the majority of people feel comfortable. The human body produces heat depending on the level of activity, and expels heat according to the surrounding environmental conditions.

The body loses heat in three main ways:  radiation, convection and evaporation. An unpleasant sensation of being too hot or too cold (thermal discomfort) can distract people from their activities and disturb their well being. This may reduce the ability to concentrate and decrease motivation to work. Thermal comfort is affected by six variable factors which are needed to maintain a healthy balance in order to sustain satisfaction with the surrounding environment.

1) Air Temperature is the most common measure of thermal comfort and can easily be influenced with passive and mechanical heating and cooling.

2) Mean Radiant Temperature is the weighted average temperature of all exposed surfaces in a room. The greater the difference between air temperature and exposed surfaces, the greater the Relative Air Velocity.

3) Relative Air Velocity (‘wind chill factor’) is the apparent temperature felt on exposed skin due to wind.  For example, if cold air is leaking in from a window, the air temperature feels lower than the actual air temperature, hence the increased likelihood of feeling cold, even when the heater is on.

4) Humidity or relative humidity is the moisture content of the air. If the humidity is above 70% or below 30% it may cause discomfort.

5) Activity Levels can reduce the heating needs, as lower air temperature is acceptable when occupants have higher activity levels.

6) Thermal Resistance of clothing or warm blankets in a bedroom can reduce the need of heating.

Building design is affected by the first four of these thermal comfort variables. The last two depend on the action and behaviour of the occupants.

What factors are influencing  thermal comfort ?
If the insulation applied is faulty or insufficient, the exposed surfaces in a room will stay significantly colder in winter or hotter in summer than the room temperature. Although the heater pumps hot air into a room, or the air-conditioning blows cool air, the thermal radiation will affect the equilibrium. The Mean Radiant Temperature is affected negatively and the occupants won’t feel comfortable.

  • The ceiling isn’t insulated or the insulation is penetrated for example because of the installation of down light. As warm air is always moving upwards, heat is lost to the cooler air in the roof space.
  • Air leakage around doors, windows, down lights, pipes, and other wall penetrations are exceeding the acceptable Relative Air Velocity.
  • Wrong application of thermal mass can influence the Mean Radiant Temperature and can therefore increase the need of mechanic heating and cooling.
  • Under- performing windows and doors (when air is able to leak in/out of poor fitting doors and windows) are also influencing the Mean Radiant Temperature and the Relative Air Velocity.

When it comes to comfort, the perception of temperature is more important than the temperature itself. For a person to feel comfortable, the difference of temperature between the head and the feet should not exceed 2.5 degrees. This demonstrates the importance of floor insulation and this explains why we usually feel more comfortable standing barefoot on carpet than on tiles.

Energy Ratings In Australia And Overseas
In Australia, energy rating assessments are done pre-construction, assuming competent application of all insulation and building materials. However, common construction practices often demonstrate misapplications and air leakages. In Europe, energy efficiency is most often assessed or checked post construction, with special attention to the prevention of thermal bridges. Some countries require airtight buildings, and amongst other things, double glazing, solar energy for hot water and heating systems, the usage of storm water, greywater recycling, recycled materials and product life cycle considerations to minimise energy demand and carbon footprint.

Conclusion
Well performing insulation and building materials is not a guarantee for well performing homes. The building envelope needs to be treated as a delicate continuous shell. Each small gap and leakage will impair the energy efficiency and the well being of the occupants. It is essential to consider the end product in order to determine how energy efficient a building really is.

House Siting & Solar Access


The siting and orientation of a building is essential in achieving good solar access and hence good energy efficiency. The house needs to be designed according to the site and must respond to site-specific conditions to maximise free solar energy. Moreover, it’s important how the rooms are arranged; the right zoning can significantly help save energy otherwise needed for heating and cooling.

Energy use, occupant thermal and visual comfort are influenced by decisions taken in the first steps of a project, usually by choices made even before the actual design begins. The selection of the site and early decisions regarding site layout, room orientation and building form can determine sunshine conditions in and around a building.

How To Optimise Solar Access
Solar access refers to the amount of direct and diffuse solar energy a building receives. Optimal solar access can improve the thermal comfort, decrease energy requirements, reducing greenhouse emission and therefore, benefiting our environment. It’s important to design your building location in order to achieve a good level of unobstructed winter sun. North-facing windows are no guarantee of good solar access. Obstructions in the form of other buildings or trees to the north, northeast or northwest can block free solar heating. The Australian Bureau of Meteorology (BOM) generally recommends that the sun should shine six hours during winter into the windows. Especially in cooler areas, the BOM also recommends solar access to east-facing windows.
New houses or renovations should always try to maximise the site’s potential free solar energy. Good orientation is a condition for energy efficiency. It is easier and more economical to consider this early in the design rather than upgrading a building once its been built. Correct siting and good solar access is relatively easy to achieve for lower density housing, whereas medium and higher density housing sometimes presents a challenge. Smart subdivisions are a requirement for adequate solar orientation and distances between buildings need to be greater to enable unobstructed sunshine into the windows.

Surface-Area-To-Volume Ratio / Building Shape
The surface area to volume ratio (S/V) is an important factor for the performance of a building. The greater the surface area, the greater the potential heat gain or loss through it. Consequently, a small S/V ratio implies minimum heat gain and heat loss. In order to minimise unwanted losses and gains through the fabric of a building, it’s desirable to design a compact shape, without articulation. In theory, the most compact building would be a cube. This configuration may not be acceptable for many reasons, such as restrictions to daylight access, site and neighbouring character, planning regulations or simply personal preferences. However, to minimise heat transfer through the building envelope, the building shape and accordingly the floor plan itself, should be as compact as possible. When designing your home consider thoughtfully what rooms are really needed. Instead of adding rooms you might need. Create multifunctional rooms, spaces that can be used for more than one function and that can easily adapt to a changing lifestyle.

House Siting
In order for a building to be energy efficient and environmentally friendly in any way, there are many things to consider when searching for a site or placing a house on a site.

Analysing needs and lifestyle – current and future

  • What type of home is needed?
    (house, apartment, villa; is a large garden required, lifestyle options and access to facilities)
  • Does the location suit your lifestyle and can it accommodate potential changes in the future?
    (family addition, retirement, old age, health and so on)
  • Is the site close to public transport, work, school, family members or other social activities?
    (Proximity may reduce the need of a second car. It will reduce car trips, travel time and carbon footprint, consequently protecting the environment, and saving money).
  • Determine the true cost of the location.
    (A site/ home in the outer suburbs may be cheaper, but will this compensate the higher transport cost and the additional times spend on the road or on public transport?)


Study the site and the local climate

  • Seasonal and diurnal temperature ranges
  • Direction of hot, cold and wet winds and cooling breezes
  • Humidity range
  • Effect of local geographic features or climate conditions, like the fall of a site, vegetation or neighbouring properties that might modify air movement and solar access.
  • Seasonal characteristics
  • Orientation of the site, determine where north is. Will the configuration of the site allow for good solar access, and the positioning of private open space and garden areas facing north?
  • Are existing or proposed buildings or trees overshadowing the site?

How to place a building
In hot climates with negligible heating needs, the building should be orientated to maximise exposure to cool breezes. The construction should aim to exclude harsh sun all year around, by minimising window sizes and/ or providing large overhangs or other effective shading devices.
All other climate zones, as well as alpine zones, need to incorporate passive solar heating and cooling. The extent of heating and cooling requirements depends on the climate. To determine if you need mostly passive heating, passive cooling, or a combination of both, you can compare summer and winter energy bills, consult a designer or an architect, or check meteorological records on the Australian Bureau of Meteorology website.
In the southern hemisphere, living areas should be ideally orientated within the range of 15°W-20°E of true or ‘solar’ north (20°W-30°E of true north is considered acceptable).  Accurate location and direction will enable standard overhangs to prevent overheating in summer and allow lower winter sun to heat the building with no extra costs or effort from the occupants.  On the other hand, a poor orientation will result in heat loss in winter and will lead to overheating in summer, by allowing low angled west or east sun to strike glass surfaces. North facing walls and windows should be set back significantly from large obstructions to the north, like trees, fences and other buildings. Keep in mind that they cast shadows two to three times their height in mid-winter. The distance to a single storey building to the north should be minimum 5.5 metres, to a double storey at least 10 metres.

  • If possible, garages, carports and other buildings or structures shouldn’t be placed on the northern side of the site.
  • Consider sharing walls with neighbours, especially on the east or west boundary as it will minimise unwanted heat loss or gain through these walls.

How to organise a floor plan
Rooms are utilised for distinct purposes at different times of the day and their placement will influence energy efficiency as well as comfort levels. Zoning means the creation of zones by grouping rooms with similar uses, and closing off unheated rooms, such as laundries or guest bedrooms, to reduce heating and cooling needs. It is important to separate heated and unheated areas with doors, such as glass or bi-fold doors to help retain the open-plan aesthetic if required.

  • Daytime living areas such as family rooms, kitchen and rumpus rooms should be north facing.
  • Avoid orientation and windows to the harsh west sun, especially for living rooms and bedrooms.
  • Locating the garages or carports to the west, east or south can protect the building from summer sun and winter wind.
  • Areas that use water (hot water in particular) should be grouped together to minimise heat loss from pipes, plumbing costs and water wastage.
  • Create buffer zones to the west and south, as this is where most of the unwanted heat gain or loss will occur, such as bathrooms, laundry or storage rooms.
  • Avoid self-shading; deep north facing courtyards, garages or other deep articulations should not overshadow north-facing windows.
  • Air-locks to external doors are essential to reduce the loss of heated air when the external doors are opened.
  • Allow for cross-ventilation. Openable windows and external doors should be located on       different      sides of the home, with less than 8 metres distance between them to create air flow.

Conclusion
If medium and high density housing is designed with careful attention to good solar access and other passive design solutions, it will use less energy compared to single storey or detached houses. The reasons for this are due to the shared walls and floors, but also the lower percentage of building envelope per dwelling, and each dwelling may have less area of external wall or roof surface. The less the outer shell is in contact with outdoor air, the less the potential thermal radiation, and therefore unwanted heat gain or loss is reduced. Moreover, a free standing home needs more construction material than high density housing and this starts an endless cycle of additional production, waste, labour and travel time.

The dream of a freestanding home is quickly becoming a distant thought; one dwelling on a block seems like an extravagance as land gets more and more precious closer to the city, forcing people to move further out into the suburbs. This leads to longer travel times, increases the dependency of cars, and consequently increases the greenhouse gas emissions through vehicles. As the population of our cities continues to grow rapidly, we have to think about alternative ways of living and have to restructure and improve our public transport system. We have to create new dreams for our sustainable future and find new ways to make medium and higher density living more desirable.
This cultural shift in how we choose to live may seem insignificant to the individual or single family, but imagine where we would end up if the majority of the population understood the positive effect of a sustainable housing model?

5.6 Stars: It’s not that hard

Now, after we have retrofitted the insulation and sealed all the gaps,  it’s time to look into other options on how to improve the energy efficiency. But also we want to optimise the floor plan.
We think there is potential to utilise the floor area more efficient. We decided to reorganise the kitchen/living/dining area and also that an European laundry would be enough for us. That means we will be able to transform the 2 bedroom unit into a 3 bedroom unit. But that’s not all, we will even manage to fit in an extra ensuite for the new master bedroom.

But what are we planning to do to that will improve the energy efficiency?

.

Air-Lock

One of the first things you should do is to put in an air-lock. With the extra door you can close of the entry area. This is especially important in Winter, then
the moment you open the front door the warm air gets sucked out and you have to start afresh. In summer it can be open all the time, but there should be a way in winter to close it off.

Replace Windows/Doors

Many might think, there is no point replacing one or 2 windows, it won’t make a difference. But you would be surprised what you can achieve. Especially big windows lead to unwanted heat gains or losses. Even just replacing some windows can make a massive difference.
We want to put in a new french door towards the new deck, also we will put in a new door and new windows in the new master bedroom. So altogether we will put in 2 new windows and 2 new doors. Keep in mind, the lower the U-value the better performing the window. In our case, we will try to get the best windows/doors we can get; double glazed, uPVC or timber windows, with a  U-value of 1.99 or lower.

Energy Savings

Just putting in the air-lock and a few new windows/doors increases our energy rating to 5.6 Stars. This means the renovated house will need 81% less energy, meaning instead of $4,300, we will just pay $829 per year.

Imagine how much energy you could save!!!

3.6 Stars: How to make an existing home more energy efficient without spending a lot of money

There are a few simple things you can do that will make a huge difference to your energy bill, without spending a lot of money.
In our case, it brings us already up to 3.6 stars. This means that we will need 62% less energy than before the renovation. Instead of paying more than $4,300 per year, we can reduce our energy bill to approximately $1,600.

So what did we do?

Seal your house

Every little gap causes unwanted heat losses and heat gains, therefore, one of the first things you can do to make your house more energy efficient are:

– Close off wall and ceiling vents

– Replace existing exhaust fans with self-closing ones

– Weather-stripe existing windows and doors

– Don’t use standard down lights in the ceiling as they leave gaps/holes in the insulation

Insulate your home as much as possible

The more insulation the better. Put in as much insulation as you can
In our case, we’re going to install insulation to the ceiling and to the roof, with a combined overall R-value of  R6.0 and insulation to the timber sub-floor of R2.0.

– Insulate the sub floor using waterproof rigid insulation and ensure there are no gaps around the insulation – for example, use expandable foam.

– Update roof/ceiling insulation using both reflective and bulk insulation, the higher the R-value the better. Aim for a combined R-value for the roof and the ceiling insulation of min. R.5.0

Retrofitting an existing brick veneer wall is a bit more tricky.  It is a pretty time intense and messy job. Therefore we decided not to insulate the walls, at least not at this stage.
Taking off the plasterboard to install bulk insulation may be the most obvious way, but you can also bore holes in between studs and pump in cellulose fibre. But if you do this you have to ensure that the walls are closed at the bottom and that the insulation can’t fall though.

3.6 stars is a good start, but we can do better.