Pros, Cons, & Costs: Hardie Board Siding
by Matt Goering
Hardie board siding, created by James Hardie and also known as cement board siding, has been around forever, but its popularity seems to come in streaks. Typically billed as a low-maintenance, long-lasting material, does it measure up to its reputation? Here are the pros, cons and costs of Hardie board siding to see how it looks under scrutiny.
Hardie Board Siding: The Pros
This siding seems to be a rising trend in the industry lately. It's a product that lasts, comes in a wide variety of textures and colors, and it's affordable. The benefits extend beyond those factors, and when it comes to hardie board siding, there is a long list of pros.
• Longevity Most Hardie board siding comes with a 50-year, limited transferable warranty. This siding is completely rot and insect resistant and can even handle salt spray from the ocean.
•Appearance Hardie board siding can be made to mimic just about any other siding material, including wood lap boards, cedar shingles, and wood shake siding. Color options are virtually unlimited. These colors are typically accompanied by a 10 to 15 year warranty on the finish.
•Fire Resistance Hardie board siding is 90 percent sand and cement which makes it fire-resistant. Case in point, a St. Paul Minnesota house fire torched two fire trucks parked 60 feet away, but the cement board siding home next door, 50 feet away, remained unscathed.
•Storm Resistance Whether you're looking for a siding material that can withstand the next Katrina, or one that can fend off the next summer hailstorm without sustaining damage, cement board siding is a proven commodity in the weather department.
What's not to like about Hardie board siding? Two things stand out. First of all, because of its weight, the siding requires more resources to install than other siding materials. Second, it's not a maintenance-free siding material. You will have to repaint it in time.
• High Installation and Labor Costs. Hardie board siding requires more planning, a larger labor force, and takes longer to install due to its composition. It weighs about 300 pounds (100 square feet) compared to 60 to 70 pounds for vinyl siding. This can increase labor and installation costs as compared to vinyl or aluminum siding.
•Maintenance. It has to be re-painted periodically. Although the warranty is usually for 50 years, Hardie board siding finishes are only guaranteed for 15 years.
Hardie board siding runs about $10 per square foot. So plan on spending about 40 percent more if you choose it over vinyl. However, if the pros speak to you more than the cons, the price doesn't matter that much.
CLIMATIC DESIGN IN HOMES
Houses in the Bahamas must respond to a hot sun, cool breezes and hurricanes. In the “old days” they were designed using elements that made living in them easier than it is today. They were cooler inside, and therefore more comfortable, and they could be prepared to respond to an oncoming hurricane quickly and easily, unlike today’s “modern” Bahamian houses. Is there a reason houses must be less accommodating today? Why are the houses designed today so much hotter and less comfortable?
The answer, of course, is that we have forgotten how to “read” the climate. For most new homeowners, the design process does not even include a discussion about climate. Questions about shade, orientation and hurricane protection are more often left to the addition of accessories, rather than the basic design. This article is to address the basic requirements of Climatic Design.
What, then, is the purpose of Climatic Design?
Importance of Climatic Design
Climate has a major effect on building performance and energy consumption. The process of identifying, understanding and controlling climatic influences at the building site is perhaps the most critical part of building design. The key objectives of climatic design include:
- To reduce energy cost of a building
- To use "natural energy" instead of mechanical system and power
- To provide comfortable and healthy environment for people
(From Climatic Design of Buildings – Hong Kong University Paper)
Energy in buildings is used to create creature comfort, which requires maintaining the temperature between roughly 70 and 80 degrees, with a reasonably low humidity. If the temperature is higher, cooling is needed, for which there are several solutions, including fans and air conditioning. Energy is also used to give light and to heat water.
The way designers use the design process to reduce the need for energy is to first reduce the heating up of the interior by avoiding insolation, then by encouraging evaporation of moisture from the skin (thereby creating cooling) using air movement (breezes). They also reduce the need for artificial light by bringing sunlight inside without its heat. Finally, they use the sun, a plentiful resource in the Bahamas, to heat water and even create an alternate source of power.
To do this, they must know both the elements of climate in the general area as well as the climate on the site. They must know where the sun rises and sets, which direction the breezes come from and when, what happens when it rains a lot, and what elements are affected by a hurricane. They must know what materials do well in humid conditions, which ones are good near the sea. They must know which trees have a canopy and which ones shed their leaves during winter.
Examples of the features of traditional buildings that respond to our particular climate are:
The high pitch of the roof, which removes the water generated by rainstorms quickly.
The Porch, which keeps the direct sun away from the openings that expose the interior of the house.
Push-out shutters, that both keep the sun away from windows as well as providing easily operated hurricane protection.
Cross ventilation, providing air movement for human cooling as well as removing stale air, improving air quality.
Raised floors cooled by breezes below.
Trellises and screens that create shade wherever needed.
Short overhang to avoid uplift by hurricanes.
Heavy planting on the west side of the house, usually with fruit trees.
Wood shingles that “breathe”, making attics cooler.
Dormers and vents to habitable attics.
Gable vents to inhabitable attics that removed warm air and left ceilings below cooler.
These are the types of concerns that climatic designers use to create buildings that are more comfortable and less expensive to use. We believe the average Bahamian building uses at least 40% too much energy. The return to Climatic Design is an important tool in the war against energy cost.
WHAT MAKES A HOUSE SO HOT?
“Boy, it’s hot! It must be 98 degrees outside. And I swear it’s hotter inside than outside.”
Many of us remember visiting our grandparents, or growing up on one of the Out Islands forty or fifty years ago, sitting at the table and listening to the mid-day news, when we were glad to be on the inside, out of the blistering sun. It was cool and refreshing inside, even without the technology of air-conditioning. Conversation would be about family and dreams, rather than about the sweat and discomfort.
Today, many of us dread the coming of summer, sweating as we sit at lunch, or as we try to sleep at night in houses that are unbelievably hot and uncomfortable.
What makes our houses so hot today?
With the many advances in technology and design, changes in the approach to design – especially in the design of the house – have led to changes in the way in which buildings perform. Two hundred, or even one hundred years ago, the limitations of technology forced designers to study the forces of nature, to use the cooling breezes and the protective features of the building to create comfort conditions. Whether farmer or fisherman, the builders of traditional Bahamian houses were used to working with the forces of nature, and creating a “cool” house came naturally to them. But those days are gone.
Gone is the ‘natural’ layout of openings to receive a south-east breeze and allow it to flow through the building, to exit at the leeward side, taking with it any build-up of hot, toxic or stale air, while cooling the bodies inside. Floor plans today rely on air-conditioning to cool and refresh the interior, and even when there is no air-conditioning, designers no longer tend to apply “cross-ventilation” principles. In any case, during the design process, their clients are more concerned about style than natural comfort. The breezes are still there, but are no longer invited in.
Gone is the use of those same breezes to cool the floors and ceilings of buildings. Traditional buildings, many with wooden floors, were often raised above the ground, with breezes flowing below, cooling the floor while preventing the build-up of rot-encouraging moisture below. The high-pitched roof of the traditional house was usually ventilated somehow, allowing the breezes to take away the hot air that builds up immediately under the roof. The ceiling below was therefore usually cool. Even open ceilings, vented above head level, were cooler than today’s fancy ‘cathedral’ ceilings, most of which encourage the build-up of heat to hang over the room. Some even use ceiling fans to spread the discomfort.
Gone are the ways of protecting the doors and windows from the hot sun, so that they remain open to receive the breezes. These were the primary uses for the porch and the push-out shutter, two elements of traditional Bahamian architecture seldom seen in so-called modern buildings. Gone with them are the complementary louvers, lattice and trellises that gave character to shading devices.
Gone is the dilly or guinep tree that shaded both the building and to the ground nearby, keeping the building cooler and making the family dinner more pleasant.
Gone is the careful selection of materials for the fabric of the house. Advances in technology have made this area more difficult, as material manufacture has become more sophisticated. For example, while it is generally true that a thick wall keeps heat out better than a thin wall, there are thin materials made with special insulation that far out-perform thick materials. There are treatments for glass that stop only the part of the light spectrum that makes sunlight hot. Some materials, like wood, perform differently in different thicknesses. And there are synthetic materials that out-perform their ‘natural’ rivals.
The Architect is therefore faced with a three-pronged opportunity to create a cooler and more comfortable house.
First, after the site has been chosen, he must familiarize himself with the direction from which the breezes flow, and '‘orient'’ the building in such a way as to receive those breezes, and provide openings that allow for cross-ventilation.
Secondly, he must provide for adequate shading of the openings and the areas near the house. Porches, shutters, and the other elements of traditional architecture should be in his toolbox as he formulates the design. He should speak with confidence as he explains to his economy-minded client that to save up-front money on these issues is a false economy, as they would eventually pay more expensive dollars for energy to cool the building, even when the conditions outside are not severe. It will always cost less to keep the sun out of the house than to cool an over-heated house.
Finally, he must select materials that promote a cool interior. Tiled floors are cooler than carpets. Wood floors are cooler in Summer and warmer in Winter than almost everything else. Exposed glass should either be treated for UV penetration or double-glazed. Lighter colored asphalt shingles reflect more of the heat-producing sunlight than dark-colored asphalt shingles. Styrofoam blocks make a great insulated wall.
This approach to the design of the house may or may not show itself in the “look” of the house – that is a matter for the skill of the Architect – but working with the climate to provide cross-ventilation, developing an appropriate shading strategy and selecting materials that help protect the house from the onslaught of the sun produces the kind of house some of us would call a dream – a house we can live in.