How Window Design Affects Energy Efficiency

Energy efficient windows play a key role in the design of green house plans. While new-age materials and technologies are essential in the creation of those windows, homeowners may be surprised to learn that style can be just as important in achieving efficiency as polymers and fiberglass.

There are plenty of window types, from sliding to hopper to casement designs. Each of these offers a different level of energy efficiency. They also serve various functions that may be more or less desirable based on homeowners' tastes as well as their building site. Here are just a few, as listed by the U.S. Department of Energy, and their relative advantages:

When a window is fixed, it means that the panes don't open. In terms of energy efficiency, they can be excellent, as they are airtight. However, they do not allow for ventilation. This design may be best served in places such as foyers to allow natural light, or as large bay windows in a living room, paired with other windows that do open. When you have a living room design such as the one depicted in this home plan, fixed panes cut down on the potential for air to leak out around such a large frame. Here a fixed pane is used as a decorative element at the top-center of the back room windows.

The panes for this design slide horizontally, and operate exactly like the sliding doors in this design. Single-sliding has one moveable pane while double-sliding has two. The appeal of this design is that homeowners can have large windows that open and close easily. However, as the Department of Energy notes, the sliding design results in generally more air leakage than other types of windows. Side-by-side sliding windows create the opportunity for more air leaks, as the design must allow space for each pane to be able to move past one another.

Like sliding windows, hung ones have moveable panes that come as singles or doubles, though these slide vertically. Because the panes are hung vertically,  they're generally smaller than those in sliding or fixed designs. As such, they're generally cheaper. They can also have comparably high air leakage rates. Hung windows have the added potential issue of gravity working against them, and it's not uncommon to see the top pane of older hung windows having trouble staying up all the way. Like sliding windows, the side-by-side design adds to the potential for leakage. These windows are among the most common in homes, as demonstrated by this design.

This type of window offers generally low air leakage rates as well as nearly unparalleled air ventilation. These windows operate on hinges that allow them to swing open horizontally. According to the Department of Energy, the higher air efficiency is due to the window closing by pressing up against the frame, creating a better air seal than sliding windows. While casement windows rest on a hinge, they can still be quite sizable and are usually installed in rooms that need lots of air and light, from the bedroom to the living room. The only downside to these windows is that  they can be heavy and put a lot of strain on their hinges, which may be problematic over time, but can be fixed. The front windows on the left wing of this modern house design may function like casements. 

Awnings and hoppers
These kinds of windows are like casements in that they swing on a hinge, though they move vertically. Like casements, they also generally boast an excellent air seal as a result of pressing against the frame. These kinds of windows are generally smaller and used expressly for ventilation. While common in skylights, they can also be paired with large fixed windows to allow for ventilation. In the design of this contemporary house plan, the upper floor front windows seem to be operate as awnings or hoppers.

What You Should Know About the Color of Your Roof

Never mind the palette for your living room – homeowners, especially those interested in green house plans, should first figure out the color of their roofs. A new study from the Lawrence Berkeley National Laboratory found that white roofs may just make for a more cost-effective and environmentally friendly house topper than the traditional black or the trendy vegetated "green" varieties. While climate change may be of primary concern for some, even those wanting to save some money should still give some thought to the roof over their heads.

The cost of cover
Berkeley lab researchers examined the three types of roofs and their life cycle cost over a 50-year period. Their conclusions were clear:

"White roofs win based on the purely economic factors we included, and black roofs should be phased out," said Arthur Rosenfield, a co-author of the paper and former Commissioner of the California Energy Commission.

According to the researchers, white roofs do a better job cooling a building and the surrounding city air than black roofs because they reflect light and heat rather than absorb it. In fact, not only were black roofs deemed economically inefficient, but also hazardous, as high summer temperatures can cause the top floors of buildings to become extremely hot.

While green roofs are similarly effective at cooling as white ones, the latter was three times more effective at countering climate change, as it purportedly kept sunlight from being absorbed into the earth's surface. Additionally, green roofs required higher installation costs than the other two kinds of roofs. Yet, the study authors also acknowledged that they did not fully investigate the benefits of the vegetation option, citing storm water management and aesthetic pleasures associated with a rooftop garden.

A grain of salt
The study seems to come down decidedly in favor of white roofs, however, Stanford research a couple of years prior indicated that reflective white actually may actually result in a net global warming due to the fact the redirected sunlight could disperse earth-cooling clouds and result in further absorption of light by pollutants. While the study did not address the potential benefit of reduced electricity bills in the summer due to a white roof, the argument could be made that those savings are lost come winter, when heat absorption may actually be a benefit.

"Cooling your house with white roofs at the expense of warming the planet is not a very desirable trade-off," said lead researcher Mark Z. Jacobson, a professor of civil and environmental engineering.

An alternative to white roofs, according to the Stanford press release, would be photovoltaic panels that generate electricity without reflecting sunlight back into the atmosphere.

Location, location, location
Conflicting research may make it hard for you to decide on your best course of action. Apart from the color, you also have plenty of materials that change the efficiency of your roofs. Additional factors such as sunlight exposure and even the pitch of the roof may influence your decision. Yet, local climate should be one of the first considerations.

White and vegetative roofs are good at keeping buildings cool, which makes them great for sunny, warm temperature climates, such as Arizona or Southern California. If you're looking at Florida house plans such as this one, you may want to consider cooling options. People in cold climates like New England, however, require heat absorption. A dark roof can even assist in snow melt in the winter months. In any case, it's always a good idea to talk to your contractor about the most cost-efficient options as well as the feasibility of implementing them.

Study Finds Owner Satisfaction With Green Homes

Green building practices make up one of the most prominent building trends of the last decade. Yet, given that the field of sustainability is still in its infancy, people may wonder just how satisfied people are with their environmentally friendly homes.

Survey says? They love it. 

A recent study commissioned by the National Association of Home Builders found that 94 percent of people who purchased a National Green Building Standard-certified home said they would recommend a green residence to a friend. An equal percentage of people agreed that they were generally satisfied with the energy performance of their homes. Finally, 92 percent said they would purchase a green home in the future. 

Energy efficient, green house plans exist in abundance for homeowners who are interested. The question remains, though, what exactly did green homeowners find so satisfying? 

Defining green 
An overwhelming majority of homeowners surveyed said that they understood what was meant by the term green home. The truth is, however, many people don't, even when they think they do. That's because the phrase is rather nebulous – it's an umbrella term that has morphed through connotations to refer to many aspects of environmentally and energy-conscious building. An environmentally friendly home doesn't necessarily mean energy-efficient, nor does either quite mean sustainability. Generally, though, green homes are a combination of all of these components – homes that are less damaging to the environment, minimize energy usage, built with renewable resources and possess a small carbon footprint. The National Green Building Standard is just one of many measures of these efforts for U.S. homes and structures.

Dissecting the answers
The survey, conducted by GuildQuality, centered on people's satisfaction with various aspects of their green homes, which are also common features of many green home plans. Air quality, water efficiency, heating, cooling and natural light were all scrutinized in the survey. Some 92 percent of respondents agreed that their home maintained consistent temperatures and were less drafty than non-green homes. A majority of 86 percent agreed that they had lower utility bills than in traditional homes. More tellingly, when asked what green features were most important in choosing or building green homes, the top answers were insulation, efficiency, energy, heating, cooling and windows. Those aspects that they were most satisfied with were low-utility bills, energy efficiency and insulation. 

Achieving green
All of these features sound great, but it's important that homeowners understand how architects and builders achieve them. While many green homes take on a modern, minimalist look, it's important to note that green building is largely concerned with design, not style. It's possible to have traditional-looking home plans that are still sustainable. Much of what makes green homes work are efficient layout, construction and Energy Star-approved products, from windows to HVAC systems. Builders of green homes usually pay special attention to developing a tight air seal and installing high-quality insulation, which cuts down on draftiness and therefore heating and cooling bills. Additionally, green houses may maximize natural heating through strategically placed windows and heat-absorbing building materials. 

Different designs
This house plan, for example, boasts plenty of green house features, while maintaining an elegant stonework design that harkens back at least a century or two. Meanwhile, this modest house plan features a simple neo-colonial style in a no-frills, high-efficiency package. In short, homeowners aren't limited by their tastes when it comes to selecting their green homes. Furthermore, even houses not originally billed as energy-efficient can still be built with Energy Star products to improve their quality in sustainability. All that's required is some forethought in the building of the home and a willingness to adjust to different, more efficient kind of living. Fortunately, plenty of intelligently designed home plans eliminate much of that hassle.