Passive Solar Part II - Reduce your home heating costs

If you are looking to build a new energy-efficient home or would like to see your existing home benefit from some much-needed energy improvements, it is important to work with an architectural designer who is experienced in passive solar design. I have designed and built many homes and remodels that see great savings in heating costs due to simple, yet skillfully implemented, passive solar strategies. The photo to the left is the living room of Liberty House, a small (why small see this link), sustainable, energy-efficient home that I both designed and built. The photo illustrates passive solar concepts in a nutshell: sunlight pours through a large South-facing window array, landing on a dark concrete floor where the solar heat is stored.

Although, passive solar design is simple in methodology, a designer who is experienced in passive solar strategies will ensure that your home's solar potentials are utilized most effectively. The key principles of passive solar design are as follows:
1. Building site properties must be evaluated and exploited.
2. The home must be designed so that it captures the solar radiation.
3. The home has a floor plan that is fairly open in order to promote convective air cycles.
4. Building materials must increase in mass for heat storage. i.e. masonry, concrete, stone, thick tiles.
5. Mass is in correct location in regards to solar aspect.
6. Windows or apertures are at right heights and face due South.
7. Building overhangs to the south are deep enough to shield the sun from the interior during the summer months to prevent overheating.
8. An aggressive strategy of cross ventilation through windows is designed into the building.
9. Windows are glazed with the correct type of glass. This type will change depending on its aspect i.e. facing North, East, South, West.

Every building site has its potentials and weaknesses in regards to utilizing the sun's energy. Sites that are sunny and fairly free of tall coniferous trees, especially to the southern aspect, have great passive solar potential. During the Summer, deciduous trees on the south side of the home help screen the sun in the summer to reduce excessive solar gain. During the colder months, deciduous trees drop their leaves, allowing the lower angled suns rays into the home.

Hills and mountains can either be an attribute or a hindrance to passive solar energy gains. An ideal situation is one where there is a hill to the west or east, but definitely not a mountain to the south. As this diagram shows, the sun angle in North America changes in its trajectory and angle through out the year. In the summer, the sun rises more to the Northeast and sets more to the Northwest. During mid day, the sun is directly overhead. In the winter, the sun moves to the South. It is due East as it rises in the morning and due West as it sets. Also, the sun angle is lower in the sky at noon, which allows maximum sun penetration into the home. A hill to the West is not necessarily bad, because the focus is to harvest heat mid-day during the winter. A hill will help keep the lower angle afternoon suns rays from penetrating into the home and reduces overheating and solar glare. This is also true for coniferous trees to the West. The same situation applies to hills and trees to the East, although it is not quite as important. In the morning, the temperature in and out of the home is a bit lower, so more sunlight not only helps to wake the inhabitant, but also helps to heat the home.

When designing a passive solar home, the main goal is to maximize solar gain to the south. The floor plan or layout is very important in achieving this. Ideally, your main open space is on the south side of the building. Having the living room, dinning room, and kitchen as a combination open space not only gives a spacious feeling, but also creates an ideal situation for direct solar gain. In these spaces it is common and sensible to have hard floor surfaces for easy cleaning. More importantly, these hard surfaces become the heat mass that capture and store sunlight from the south. Usually, more open living spaces allow for enough solar gain to occur and with a good layout, furniture can be kept clear of these surfaces. Note: Darker floors will increase gain, lighter colors reflect the radiation, which is not desirable for solar gain.

Making direct radiant gain work is dependent on the flooring mass. It is important that window heights are close the floor, so that the sunlight falls directly on it, without being blocked by soft-scape obstructions like sofas and chairs. Tables are okay because the sun usually will filter around the table legs. It is important to avoid floor rugs in this area. A minimum of 1.5" of concrete slab thickness as the flooring works very well because it holds sufficient heat. The slab can also have radiant hydronic heating coils, or "Pex," laid into it. It can be applied over typical 3/4" plywood subfloor as long as the joists span meet the increased load rating. On some South-facing floors, it is possible to pour slab on grade if the elevation of the building works out correctly. This can be poured up to 8" thick, although this is considered almost wasting material. The slab must be insulated to the ground with hard insulation or the floor will wick cold in and heat out. Proper insulation below such radiant gain surfaces is a must. Again, heating hydronics in a slab makes sense because relying solely on the sun's energy can be difficult when the sun doesn't shine for extended periods of time. Through combining passive solar heating and hydronic slab heating, there is much to be gained. Hydronic coils bring heat back into the system, which flows throughout the floors of the home, helping to reduce the need to frequently run the boiler. If relying on mass alone, it must be thicker. I know folks who live in Northern climates that rely on an insulated 6" concrete slab with southern glazing and just a wood stove. They live very comfortably through the coldest months. The concrete slab stores solar heat so well, they often don't have to light their wood stove for days.

How the mass works to your advantage has to do with its ability to store the heat and then emit it throughout the night-time hours. If concrete is not a desired interior floor, it can have masonry tiles or stone laid over it. Even a typical plywood sub-floor with 1/2" of durarock then overlaid with tile is better than no mass at all. This is common in remodels of homes for achieving more radiant gain.

As said before, it is preferable to have the windows close to the mass floor as this gets the sun's radiation to land directly on the slab closest to the glazing. It is advantageous to use specially-designed glazing on the South side of the home. Double layer thermal pane glazing with a low emissivity coating are the norm for passive solar gain (L-e 173). Note: The higher the Low E number, the less solar heat gain you will get, but it will have better U-value, or insulative properties. Higher series such a 300 and up Low E is preferable on the aspects of the building where one wants to reduce heat gain, increase insulative properties, and reduce ultraviolet radiation destruction of furniture and soft materials.

Cross-ventilation in a passive solar home is very important. Height differences of walls across the room promote cooling and air convection. I found that by having awning windows low to the floor on the South-side and a high awning windows on the highest walls, helps to promote a air draft that encourages air flow and convective cycles. The advantages here are very important because in the summer it encourages passive cooling or evaporative cooling. This is free air conditioning. Air pressure differences due to hot and cold differences in the building allow heat to escape through the awning windows. Air inlets create an upflow that encourages evaporation of moisture on our skin and gives the sense of cooling. Rather than spend a bunch of money on air conditioning, spend the money operable windows and a home designer with experience in convective design. You will save you money in energy costs!

In a nut shell, a home does not need to employ expensive and energy-consuming mechanical systems in order to heat and cool. The heat gained from a passive solar strategy will reduce yearly heating costs. By hiring a skilled designer to properly configure glazing, ventilation strategies, window layouts, and appropriate flooring mass, it IS possible to achieve a net zero home heating system. At Greenovision, we are passionate about passive solar design and other energy-efficiency systems and have a lot of experience implementing these strategies into new and remodeled homes. Please come to Greenovision for see how how passive solar design can save you money. See reasons to get off the corporate energy grid on my blog Part 1 of Why Passive solar?.

Why Passive and Active Solar Design? - Part 1

Homes over the last 70 years have been built to rely on the grid system. Big Utility companies or corporations have had a bonanza with making home builders think this way in order to gain a monopoly on energy sales. However in order to move into an energy independence mode we need to rethink this antiquated system. The grid system has many disadvantages today.
The image above is of a liquid solar array on my neighbors home, Adrien Tanguay, who installed this system, he works in this field.

Grid system energy has relied on several factors and lies. Factor and lie #1, cheap energy. Cheap energy is a lie because there is no such thing or "you don't get something for nothing". Energy in America has been cheap while it was new in the finding. Coal, natural gas, oil when first tapped were cheap because the extraction was easy, at the surface, and there was lots of it. Today we have misused these sources of energy by overly relying on them and to the point where not only have we hit the down slope on oil well reserves but we have also destroyed huge tracts of land in order to mine and extract these resource. Of course big utility corporations have enjoyed their boom years and have hijacked the way most view energy.

Lie #2 is that energy inexpensiveness has not cost something. We have entered a time period of "Global warming" no matter what the corporations would like the general populace to think. Fossil fuel burning has led to the destruction of our atmosphere and in a very short 200 some odd years. At this time we must slow the singular reliance on these non renewable energy sources. Grid system methodologies hide facts about the dirtiness of their production. Because we cant see the massive energy plants we don't see the dirt, but our environment does and its sending us some clear messages at this time.

Lie #3 : Grid transmission of power is cheaper than making it locally. Grid transmission is only cheap because of mass numbers of customers, that is what makes it cheap as well as our good old federal government subsidizing such power for many years through breaks to the utility companies. These breaks are coming to the end with the E.P.A starting to send clear signs that stripping coal and new off shore oil wells will not be tolerated. So the resources will become more expensive and utilities will charge more in the future. Cheap electricity has relied on coal. Coal will become more expensive, and the burning of it to generate energy will become more expensive as the EPA cracks down further on emissions standards of carbon dioxide from these plants.

Lie #4: Local power production is unsightly, and noisy. Windmills, solar collectors, and wood burning yes have impacts but so has the grid system. Miles and miles of overhead power lines litter the roads, even woods, fields, and blight the landscape as a whole. At this point most of us just ignore it and don't see it because who really wants to acknowledge it. I guess we have gotten used to it in the very brief time since its introduction a century ago. But what we do recognize are things that are new.... and wind mills and solar collectors are relatively new... so we see them, but I would argue this is just for awhile... once homes employ their own generation systems they will not be so alien to us. Have you ever heard anyone say "wow those power towers are lovely"?

Lie #5: Local power production is more expensive. Well it is and it isn't. Much of the expense has to do with local resource availability. Heating by wood stove makes sense in areas that renewable wood sources are plentiful. Wind produces electricity makes sense where there is wind. Solar electric power and passive solar heating make sense where there is ample sun. There are combination of energy gathering systems where the region has a little bit of both. There are other energy sources as well locally available that we do not use due to our dumbed down monolithic grid system energy reliance. The expense often comes in hiring experts to assess the needs of a home in power and which systems make sense in the making of it there on site. The apparati that make the energy usable on-site are initially expensive due to installation and material but the life cycle cost brings this down over time. If our government would subsidize this type of local energy production rather than the corporate energy I would say it would in the end "pan out".

Grid transmission of energy is fairly inefficient when you look at the losses of energy over the lengths of the power lines or 6.5% in 2007. The infrastructure is also expensive in cost, material, and unsightliness. With increased needs throughout the USA electric transmission can be unreliable found in the form of Black outs. Oil, natural gas all require shipping which is dependent on cheap oil which as we must realize will run out.

Pluses on localized energy production and utilization are that it uses locally available natural and renewable energy resources. It promotes and creates local jobs involved in home energy assessment, installation, manufacturing, harvesting of wood, and design. Using local energy keeps home inhabitants connected to their energy consumption which often promotes energy saving. When home occupants have to think directly about their energy usage they tend to me more frugal whereas with grid type energy and petro/gas utility purchase power it is more abstract by being reduced to dollars. A simple example of this is wood heating, home owners that heat with wood have a pretty good idea of how much wood they need to cut, stack and split in order to make it through the winter and they typically are good at rationing the usage of it. See my blog on radiant heat wood stove retrofit. Oh by the way some might argue that wood burning is dirty... modern wood burning boilers have come along way and do meet EPA standards see this article.
It is easier to make small energy systems less impactive because they dont require train loads of coal. Some might argue that each one of the energy producing systems need to be manufactured. This is true but with simplicity there is less infrastructure, my belief is that it balances out over shipping and grid transport. Also in this same vain your home already has furnaces, meters, wiring, etc its just that its not set up to utilize energy found nearby.

My next blog will deal with passive solar and implementation in the home. See write up here

Wood stove heat exchanger , pretty hot

Just wanted to report some news about my Brothers shop that I designed and built called Werkhaus... see the project here
Yep my brother has finally finished off the heating system with the help of Norm Walters, a radiant heating tech, its kind of exciting because its the final product of a giant experiment started about 4 years ago. To give the overall picture of the scheme of the heating system please see this pic first, oh and this one too they diagrammatically says a lot about the general idea we had years ago.
Originally we started with radiant heat tubing in the concrete slab, and phil used a wood stove up till this fall to heat the building using the fan systems to move heat around the building. This really was lacking though because Phil has to work on cars while on a dolly on the slab...really kind of cold down at that level. So he knew that getting the slab up and running as the heat source would be the ultimate solution.



Phil is on a budget so a typical on the wall, on demand propane condensing boiler was out of the question, at least for now. Originally Phil and I came up with an idea...What if the wood stove came with a heat exchange manifold? Would this do the trick and provide enough heat to run the slab? Well the answer is yes, but it isnt quite that simple. Norm Walters filled Phil in on the possible scenario that might make it all work. What it comes down to is you need a tank to store the heat, and this tank it was decided needed to be well insulated and preferably do some heating too. So a couple of years ago Phil purchased this unit
Then he had Norm hook up his wood stove which came with a very simple heat exchange coil by using a typical manifold and pump system like this.... Well to make along story short... he got this hooked up to the slab with a typical manifold system and ran it straight off the wood stove but guess what? It just wasnt enough of a heat coil on the stove to make it work or run warm enough. So he resorted to running off the electric hot water heater , and guess what... his electric bill went nuts. So Norm found a copper coil from some old refrigerator unit and installed it on the top of Phils wood stove to increase the heat capturing capability of the stove and water tank. I am making this sound all quite simple but in reality... it took some fiddling and some pumps, and guages, and sensors, thermostats, and electric meters to make it all work, along with some rather confusing diagrams...I cant figure it out too much but what I do know is that Phil is quite happy with the fact that he is running his concrete slab with the wood stove and looks to save some electricity this winter... he sounds kind of excited about it and I would have to say that makes me happy... With some work it is possible to make these systems happen, and it does help to have a radiant heat techy on hand like Norm.

See if you can figure it all out from the the pictures I provided. I understand the concepts but and not really on top of the electrical and plumbing part.

Why small homes?

Why build a small(er) home? In America, historically there has been plenty of space to work with, which has set up the paradigm that 'big is better'.  Currently, the norm in selling homes is by advertising floor plan square-footage and numbers of bathrooms/bedrooms. This is a vague way of describing a home and lacks many truths about what actually makes a home appealing , healthy, and affordable. With land values escalating, building materials and labor costs increasing, and energy costs on the rise, big houses become a burden. Small homes are the future of home construction. Affordability, coziness, and sustainability are achievable in small homes.

Small should not bring thoughts of cramped, compartmentalized, stuffy places. Small in floor plan can feel large spatially if properly designed and laid out. Some attributes that make a home intimate to the inhabitant are:                   

1. The design layout and how the inhabitant uses the spaces.                           

2. How volume influences perception of spatial scale, either cozy or grand.      

3. Crafted details of the home and how they influence how the inhabitant feels.                                                                                                               

4. Window orientation has a significant influence on how we feel within the home, but unfortunately, natural lighting and views are often left out of the picture in home design.  

Plan of 1400 s.f. passive solar 'Liberty House'

When a home is reduced in scale, it becomes manageable. Infrastructure scale/sizing, material consumption and associated waste reduction, natural lighting or day-lighting transmittance, heat transfer, building lot size and town setback requirements, roof water shed or run-off, and energy demand are easier to analyze in a small home.

   

Infrastructure scale pertains to utilities like heating, electrical, plumbing, and communication networks. It may seem obvious, but the escalation in building scale increases the lineal footage of communication cables, waterlines, sewer, venting, electrical lines, roof gutters, and even walkways. Every one of these infrastructures, when reduced in scale, simplify design and construction in time, cost, and technology. What this means is a trade off: less infrastructure, more budget for the aspects of the home that make it client specific, comfortable, and beautiful.

The scale of the home directly relates to the lineal footage of construction materials that are both hidden and exposed. More wall length and floor area equals more roof area. A large home can lead to a runaway budget. Every single exterior surface needs to be insulated and the interior covered with finish materials. In many larger homes, building materials are cheapened in order to bring the budget into check. Instead of being built with beautiful and durable materials, large homes are constructed with cheap, generic, and short-lived materials. 

The interior of a large home often suffers due to budget. Generic usage of cheap materials like drywall or paper based window, door, and baseboard trim are what the inhabitant lives with. Certainly, the flooring/carpeting will not be of any longevity either in order to cover the many square feet needed. For example, Pergo may look like wood, but it is just a very thin veneer of wood over paper, which when wet will expand and fall apart. Most of these cheap interior products not only look fake with fake wood grains and textures, but are also unhealthy. Most of these products are filled with glues and toxic resins. They usually are not meant to be left in their natural state and must be painted in order to look good.

One of the largest expenses in home construction is labor. Cheap materials require initial labor to install.  Sadly, due to their short life cycle, more labor is required down the road in order to tear them out and reinstall once they fail. This is where a huge compromise is made with most modern, large-scaled homes. Cheap materials are wasteful not only because they fall apart and must be replaced, but also because they are mostly non recyclable. "Built to last" is the way to save money in the long run; this requires using quality materials and construction methods. Reducing a home's size makes a "built to last" home possible to build without taking out huge loans. Quality materials look better and can be crafted rather than 'installed' to give a home unique and lasting qualities. Certain materials carry not only visual impact, but allow the home to function more efficiently. For example, designing a stained concrete floor into a home not only adds to the durability of the floor, but offers mass for a passive solar heating strategy. Stained concrete floors are attractive and do not require additional flooring, reducing the total materials needed.

Rufus the cat loves radiant heating

Smaller homes, compared to large homes, share natural light better across the building, especially if the main living spaces are kept open. In large homes, natural lightly is usually  cut up or blocked by walls and compartmentalized rooms. A lack of natural lightly and views of the outdoors causes rooms to feel gloomy and requiring more electric lighting and associated infrastructure.   

Daylight and views present everywhere in this computer simulation

Views and daylighting

A smaller home footprint reduces spans of rafters and joists, eliminating the need for midpoint bearing walls. With fewer walls, window views and natural light are shared across the building, reducing electric lighting energy. Living in small home with well-placed windows allows the inhabitant to feel more connected to the outdoor environment. Window views can be arranged to connect the inhabitant with trees, sky, and wildlife. Window views provide the home with 'natural decoration.' Natural light also tends to kill mold and mildew, due to its ultraviolet wavelength.

Passive venting or across room airflow= cooling

Having fewer walls also encourages airflow throughout the home. Air movement, or convective cycles, keep the building fresh and not as stagnant, creating a healthier environment for the inhabitant. Air convection set up by heat and cold promotes an even heat exchange throughout the building without the need of fans or air-conditioning apparatuses. During the hot summer months, windows around the home can be opened to create a pressure difference across the building. This pressure difference is due to heat differences between the sunny sides and shady sides of the building. The pressure differences set up a small airflow and encourages evaporative cooling.

Large homes require more windows and doors, which are one of the more costly materials in home construction. Because of this increased cost, builders often install 'economy' windows and doors that are made from cheaper, less environmentally-sustainable materials (such as vinyl with inferior gasket systems). Because a small home intrinsically has fewer windows than a large home, quality, energy-efficient windows can be purchased and designed into the building. Although more expensive up front, quality windows and doors ultimately save on home energy expenses.

When choosing to build a small home, plan to build small with the option growing as your needs and budget grow. Plan to save materials before the home is built. Plan on using quality recycled materials by designing them into the home and saving them before construction begins. Building an affordable, functional, and beautiful home is all dependent on design.  

As one can see, there is truth to Ludwig Mies van der Rohe's expression "Less is More". In this time period with rising materials and labor costs and energy becoming more expensive, small homes make more sense than large, cheaply-built, inefficient homes.

Metal Roofs: The Sustainable Roofing Choice

 
In a previous blog post, I discussed the many cons of asphalt shingles. Now I will discuss a better alternative to asphalt shingle roofs: Metal Roofs.  Now I know some will say that metal roofing has high embodied energy and is not on the sustainable list, but I have to disagree because it last or out lasts probably 3 of 4 even more asphalt shingle reroofs, this is a serious consideration.   Greenovision believes strongly in metal roofs as they last very well, sometimes up to 100 years. The thickness of metal is important- thinner sheeting will dent if large hail hits, which as the climate change is suggesting, will occur more frequently. 24 gauge is heavy; 26 a bit thinner, but both will work fine.

I like standing seamed panels that are 18" or less; they will not leak if detailed correctly.  A panel larger than 18" will oil-can when it heats and cools. Expansion is an important consideration, but more metal roof companies are well aware of this and it is mostly a problem in very large roofs.  This image shows additional panel structure or striation to help avoid oil canning.

Depending on where you live and the type of home you have, but may have Historic Preservation rules. Historic Societies sometimes make a big deal about metal roofing not matching the existing vernacular, which in many very old homes is often slate.  Slate roofing is excellent, but very expensive.  Unfortunately, Historic Societies consider asphalt a reasonable simulation in look, but they never consider its longevity.  If you must go this route a simulation slate from Eco Star   is a 50 yr product that is made fro 80% recycled materials consisting of old tires and plastic.  From the look of it on my neighbors home it has handled hail very well and looks better than asphalt , it does look like slate.  I have never used the product but I think I would it I had to. Below is a picture of it on my neighbors home Adrien Tanguay.

When considering using a metal roof, it is important where the snow will fall once shed from the roof.  Metal roofs eliminate snow as soon as there is a melt and when it slides off, it usually does so in one giant avalanche. Below is an example of snow shed from a metal roof onto an awning and then from that.  It can really pile up.

There are snow guards that can be installed to the roof that hold the snow so that it doesn't fall on a walkway or door way all at once.  These work well in that they allow the snow to melt on the roof in areas of concern.  There are different styles of snow guards.  Gutters often need to be installed in these places. If your home has problems with ice damning, metal roofing will help solve problem because ice cannot cling to metal as it does with asphalt shingles.

Metal roofing comes in a wide variety of pleasant colors to match details of your exterior.  Most metal is a galvanized steel aluminum alloy, which resists rusting. The color coatings need to be quality. Anyone that gets on the roof should be careful to not scratch it as metal is very slippery and is not as attractive when scratched. 

Metal roofs cost more up front than asphalt shingle roofing, but because metal last much longer than asphalt shingles, the home owner ultimately sees huge maintenance savings. Also because metal lasts longer, it is a much more sustainable and environmentally-friendly alternative to asphalt.

Here is a company that shows some images of metal roofing and application. If you have any questions about my experience with metal roofs, please feel free to contact me.

Asphalt shingles: What's wrong with them?

Asphalt shingles: the unsustainable roofing choice. Studies show that climate change will cause stronger and more frequent hail storms and other weather patterns. With hail the size of golf balls, asphalt shingles don't stand a chance. The numbers of homes in Bozeman, MT that have been re-roofed since the devastating Spring 2010 hail storm is a message to local builders and homeowners that this product is not a cost-effective roofing material. 

Asphalt shingles are unresistant to hail and dramatic temperature changes. They only last an average of 15 years. When old, nonfunctional shingles are removed from a home, they usually are not recycled and end up in landfill. "The amount of asphalt shingles that goes into landfills on an annual basis is approximately 7-10 million tons." If asphalt shingles are recycled, the recycling product often is not safe nor environmentally-friendly For example, one recycling company sold tons of mulched asphalt shingles for landscaping. "In 2004, the DEQ determined that the mulch contains toxins such as arsenic arsenic and polyaromatic hydrocarbons in concentrations higher than those considered safe for soils at residential and commercial settings. The agency directed Darold Smith, owner of the Springfield manufacturing site, to stop selling the mulch to homeowners and nonindustrial firms" Read more about that here: http://www.articlesnatch.com/Article/The-Dirty-Truth-About-Asphalt-Shingle-Roofs/670123#ixzz13NkvJouD

DEQ

Abbreviation for the Incoterm "Delivered Ex Quay."
..... Click the link for more information.

Many builders that advertise their company as "Green" frequently install asphalt shingles. I find this to be highly contradictory. The health aspect of asphalt and fiberglass shingles is also questionable. People who install shingles are at serious health risks. "Fiberglass shingles have a base layer of glass fiber reinforcing mat. The mat is made from wet, random-laid fiberglass bonded with urea-formaldehyde resin. Fiberglass reinforcement was devised as the replacement for asbestos paper reinforcement of roofing shingles." By tearing, cutting, breathing, and handling shingles, workers are exposed to carcinogens. Asphalt itself is a dirty industry based on petroleum and its associated distillates. The off-gassing of such additives occurs when heated. According to the warranty on the shingle packages, the shingles must not be laid in the cold, meaning that they should be installed when its warm. That's when the shingle heats up and starts to off-gas. Many shingles are now made with a mild algicide and/or fungicide. Usually this is a copper compound, but may be a more complex chemical.The health effects and stats can be found here.

"WARNING: The National Institute for Occupational Safety and Health (NIOSH) has concluded that fumes of heated asphalt are a potentialoccupational carcinogen. Do not burn asphalt roofing products."

How long do asphalt shingles really last?  The shingle companies claim that asphalt shingles will last 25 years, however, they also explain that this warranty is under ideal application, location, temperature, and installation practice.Studies show that shingles do not last as long as the roofing manufacturers claim. "According to the insurance industry, an asphalt roof that is over 17 years old has zero value in the event that there is a loss. The insurance industry has also stated that there is no reliable testing that has been done on these products. " Asphalt shingles usually last longer in cooler climates than warmer ones. Thermal shock, when the ambient temperature changes dramatically within a very short period of time, is damaging to the shingles. Read more about longevity here: http://www.articlesnatch.com/Article/The-Dirty-Truth-About-Asphalt-Shingle-Roofs/670123#ixzz13NoL97QF

Frequently re-roofing your home ultimately causes your roof to leak. When nailing down asphalt shingles, the roof boards or under sheathing are perforated with a nail nail every 8 -12 inches. Rather than protecting your roofs, installs asphalt shingles just adds more holes. When your shingles fail and the roof is leaking, it is very difficult to patch the roof. Usually, a leaky, overly perforated roof must undergo a complete re-roof, which is an expensive project.

So, what is good roofing? Read my follow-up post that discusses Metal Roofs: the sustainable alternative.