Posts Tagged ‘Solar’
It was very exciting yesterday to attend the 2nd annual regional meeting of Passive House Northwest held at Evergreen State College. Last year at the 1st one, we had about eighty people attend. This year my guess would be well over three hundred. This didn’t surprise me because the movement is really picking up steam in the US. And why not, who doesn’t want to live in incredible comfort, have a home with minimal carbon foot print, as save a ton of money in the process. And because they are so energy efficient they only require about a quarter of the solar panels of a code built home, to supply all of you energy needs. Imagine never haveing to pay a power bill again.
The conference featured several talks on methodology, along with case studies of actual homes that have been built in the northwest. The speakers ranged from building scientist, builders and passive house consultants, to even the home owners of Passive House’s. The talks were very detailed, and incredibly informative. Also there where many vendors promoting the latest advances in things like windows, Heat Recovery Ventilators and air sealing tapes and fabrics. For me the most telling reason of why this is the right approach to home building was hearing the home owners, the folks who actually paid for and live in the homes, explaining how wonderful there new homes where.
I celebrated having attended the conference by meeting with my design team and the homeowners of what will become our first Passive House. We settled on a floor plan and will meet at the Patterson Lake site next week to review elevations and exactly how the home will sit on the sight. It very exciting and I will try to keep you updated as we move through the process.
1. Shades, Awnings, Blinds, Curtains and even foliage around the windows can affect solar heat gain and can also be a cheap way to cool the house.
2. There are five parts of a window that affect its energy efficiency: Glazing technology; Frame; Operating Type i.e. how it opens and closes; Low-E coatings; Gas fills; Spacers. You need to check all these aspects of a window and ensure that they are the best suited for your climate.
3. Depending on the kind of problem you think you’re likely to have, focus on each of the six parts mentioned above. For instance:
a. If you live in predominantly warm and sunny climate, then you will need to focus on Glazing, Low-E coatings
b. If your weather is humid, then attention to spacers, frames and operating type will keep condensation and leakage problems in check
c. In cold climates, glazing, frame, spacers and gas fills need to be checked well before buying
4. Energy-efficient mortgages are a way of paying for energy efficient windows, which typically cost more than regular windows. This actually turns out to be quite cost effective, because the savings on energy and utility bills arising out of energy-efficient homes offsets the monthly mortgage payments. To get more details, visit the energy department in your state.
5. Important: Get your energy efficient windows installed by a professional. If not installed properly, they will be less efficient than even regular windows. . Make sure your installation expert has experience in installing windows and is familiar that particular manufacturer.
It is very evident that the larger your window, the more natural light it will bring in. Depending on the positioning of your windows, and its visible transmittance (VT) value, your windows could provide you with enough natural light to greatly minimize if not eliminate electric lighting requirements during daytime.
VT values are generally given between 0-1. A rating of over 0.70 is the highest you can get with clear glass windows devoid of any coatings or tints. The more the number of panes, coatings and tints the lower the VT value.
A high Visible Transmittance has another advantage – it eliminates the cooling function which is usually required in a house that uses electric lighting. A high VT value is especially important when a home is built using passive house principles or design.
However, one thing to consider when it comes to VT, is that a window with a high VT value, will also admit that much more solar energy (heat) inside the room. Thus, a clear glass window with a VT of 0.8 will also have an SHGC of over 0.60 – something not at all desirable in a warm or sunny climate.
To get around this, one can use Low E coatings, which are invisible, and yet block heat gain considerably. These coatings also protect indoor furniture and upholstery from the damaging effects of UV rays. Another way is to have operable windows that you can open up to air the room out frequently. Needless to say, a good ventilation system is important when you have large windows and a sunny climate.
For windows that are low on SHGC and high on VT, look for a high Light-to-Solar gain ratio. This determines how much more light is let in without adding to the heat.
There are two ways that windows help in heating and cooling – by preventing heat loss from the room, and by taking in heat from the outside. The former is measured by a window’s U-Factor and the latter by SHGC. U-Factor measures how much heat is lost through the window. The actual math gets quite complicated – U-Factor tells you how much heat is lost in one hour for one square foot at a certain temperature. A low U-Factor value (usually of 0.35 or lesser) means less loss and thus better insulation. Conversely, some windows may even mention an R-value, which is a measure of insulation. A low U-value corresponds to a high R-value.
SHGC is a value between 0-1. The lower the value, the less the amount of heat a window admits. Depending on the climate and your heating/cooling requirements you will need to pick a window with the right combination of SHGC and U-value. In cold climates, you want a U-value lesser than 0.35 combined with a high SHGC of around 0.60 or higher. This will considerable reduce the load on your heating system. For warm climates, you want the opposite – a low SHGC of less than 0.40 with a high U-value.
Does this mean you will have to change windows to match the seasons? Not necessarily. A metallic oxide layer (called a low E coating) applied on the outside keep the heat out, lowering the SHGC and when applied on the inside decreases the U-value. Even tints work well, though they only reduce the SHGC value.
Does material matter? Very much so, windows made of wood are not very good on insulation, while vinyl and fibreglass frames have the lowest U-values. Metal should be your last option when looking for insulation.
There’s quite a fraction of people reading this series on LED lighting who will nod their heads in disagreement. You’ve probably heard from your friend’s that they are very-expensive, very-chic, or that LED installations go bonkers after a few months. The problem is not with LED. LED is one of the best lighting options for residences, when used correctly. An inexperienced electrician and incorrect buying decisions can do a lot of harm to the lighting of the house, to you and your pocket. Here’s what to bear in mind:
1. Buy the right type of LED for your requirements. There are low wattage LEDs, which will work on 1mA (very little) of electricity and there are also new High-Power, high wattage LED which will work on more than 1A (100+ mA) and produce over 1000 lumens. The low wattage ones are used singularly to create different effects, usually for decorative purposes. The high wattage ones are used in place of a light bulb, or used in an array to provide enough light for an entire room.
2. Both types of LED lighting have different requirements. Low wattage LEDs burn out very quickly if not used with the right kind of voltage. They require much less than what is available by default in homes. High wattage ones, on the other hand can work with what we have in homes but need adequate heat sinks that will absorb the extra heat they will produce. If heat sinks are damaged, the lighting will burn out in seconds.
3. LEDs are quite affected by ambient room temperature. Installing them into walls which are not properly ventilated or in rooms that tend to get warm affects their life expectancy, causing them to fade out faster.