It would be impossible for us to cover all of the building materials on the market in this article. Now that we have described the main considerations for selecting building materials, it is necessary to put that into context for each type of material. We are going to look at the major building component categories and attempt to provide that guidance for each, starting with the outside walls, foundation and roof and work our way in.
Remember to focus on the primary function or performance that you need from the product, as well as any concerns from using it. All materials used within the walls of your home and as interior finishes can have health impacts, while others may have environmental impacts. In our discussion of materials in this section, we will just acknowledge in which product categories these considerations are important.
Foundations and Hardscapes
We want strong foundations, and they should be designed for your site, so this means boring soil samples and engineering accordingly. Which type of foundation is right for you will depend upon your site and soils. We tend to prefer pier and beam or basement foundations as they are much more material efficient than a slab foundation and provide the ability to access plumbing as needed over time for repairs or renovations. If radon, a deadly radioactive cancer-causing soil gas, is not present in your area, you should consider installing a moisture barrier over the soil and sealing up the crawlspace and installing insulation at the foundation walls. If radon is present, you should ventilate that assembly with an exhaust fan to create a negative pressure between the crawlspace and the house. If you go the slab route in a risk area for radon, you’ll want to install a radon ventilation system as part of your foundation design.
Also, if you go the slab route, consider stepping the foundation for any major changes in grade, as this also will reduce the amount of materials required. We’ve seen foundations drop 17 feet off the side of a hill, taking a lot of concrete and fill to assemble. If you must install piers or footings anyway, better to use beams for floor support and then enclose the parameter with ICF panels (insulated concrete forms). This assembly creates a great storage facility that can be used as a mechanical room.
Make certain that your foundation contractor reuses old form boards from one project to the next. There is no reason to see this lumber go into your trash bin. Also, your contractor should be using non-petroleum-based release agents on those form boards, as the substance that keeps the concrete from sticking to the wood. This alternative product will not leach toxins into your soils as it is washed off. Also, remember that the concrete sticks to the inside of the truck, so when the truck driver washes out the tumbler, this sends toxic chemical binders into our soil and eventually water systems. There are concrete washout systems that can be used to treat the wastewater and reclaim any aggregates from the waste.
When you can, limit impervious surfaces, including driveways, walkways and patios (hardscapes). These areas reduce the land available for precious rainwater to infiltrate onsite, providing natural irrigation. Consider permeable alternatives, such as permeable concrete or pavers. With these materials, you must make sure the contractor prepares an aggregate bed, per manufacturer’s guidelines, and protects the area from future contamination that can be caused when erosion carries soils, compost and mulch materials over the surface, as these can clog up the drainage.
Finally, choose light-colored materials for all outdoor hardscape surfaces to reduce the urban heat island effect. If this is not possible, plant fast-growing shade tree species that will provide shading to these hardscapes within five years. Shade arbors and pergolas also can be used as shading devices for the hardscape, as well as providing a shade buffer zone for the adjoining side of the house.
Structure
We want our structures to be durable, low maintenance and have high thermal value. The framing materials that you select should provide a good thermal envelope and be resistant to pests and weather damage. Remember to refer to your risk assessment that was discussed in Equipment & Systems category to determine which materials and systems will address the risks likely for your site over the life of your home. Special materials may be required if you are building in areas with concern for hurricane, tornado, or earthquake activity.
There are numerous choices that you can utilize to achieve a darker shade of green on your project, including improved framing techniques, engineered products, as well as alternative and natural building systems. The latter two are both resistant to weather and pest, as well as providing exceptional resistance to fire, mold and seismic risks. These are durable, long-life expectancy systems with high thermal and acoustic ratings and will be discussed further after we look at traditional framed structures.
- Sustainable Framing Materials:
The majority of all homes built today are wood framed. When selecting wood products, it is important to rely on credible third-party certifications for lumber sources. The two main certification entities are the Forest Stewardship Council (FSC- stamped wood products) and the Sustainable Forestry Initiative (SFI-labeled products). FSC-stamped wood products are harvested from forests managed according to the guidelines of the Forest Stewardship Council, a non-profit organization. This means that trees are harvested under strict regulation, respecting the rights of indigenous people and laws of forest lands, that fair trade practices protect local economies and that seedlings are replanted to replace what’s harvested. These products require a chain of custody, meaning that every entity that handles the product from the time it is harvested until it is delivered to your jobsite is certified to assure that program requirements are met. Compliance is verified by audit visits. SFI products do not carry a chain of custody; while compliance with their guidelines is voluntary and not subject to the same verification audits, the intent is similar.
- Engineered Products:
When it comes to structural members, engineered products include glue-lam beams and headers, as well as roof and floor trusses. They are engineered for strength, so they are a great alternative to solid sawn lumber that requires older-growth trees. Other engineered products include finger-jointed studs and trim and oriented-strand board (OSB), and medium density fiberboard (MDF).
The engineering design of all of these products provides significant improvements in structural stability, as the products are straighter and have fewer defects. Since knotting and grain abnormalities have been removed, you don’t get the twisting and warping problems associated with solid-sawn lumber that resulted in structural and cosmetic problems over time that take more resources to repair. This means that even though some of these materials may carry a little cost premium, they result in having to use less structural framing than when solid sawn lumber is used exclusively, resulting in no net cost premium. In fact, using engineered trusses and wall panels can reduce the amount of lumber required by 25-35 percent and the time spent by 30-50 percent, resulting in a net cost savings of 16 percent over conventional framing.
- Metal Framing:
As an alternative to wood framing, metal offers long-term durability and resistance to weather and pests. Metal is energy- intensive to produce, but it is infinitely recyclable. However, since thermal performance is one of our primary objectives, it is worth noting that metal is a great conductor of heat. Since framing makes up about 25 percent of the exterior of your home, steel will conduct about four hundred times as much heat into or out of your home as wood framing does. This can reduce the average R-value of the wall as a whole by over one half! To reduce thermal bridging when using metal framing members, it is important, and required by the building codes, to use an insulating sheathing continuously around the exterior of the home. (Note that wood framing is also subject to thermal bridging, so using a rigid foam sheathing on top of your structural sheathing is always a good idea). The thickness of the insulating sheathing foam is dictated by the severity of your climate (and is specified in the building or energy code used in your region) with ranges from half an inch to two inches, with a minimum of R-4.2 required even in the most hospitable of climates.
- Natural Building Systems:
Natural building systems have been around since life began on Earth. Just as birds build nests from sticks and feathers, man has constructed shelters from combinations of earth and vegetation since we migrated out of caves. These types of structure have evolved throughout history based on what materials were available locally, the skill sets of indigenous people and, of course, trial and error to address various previous building failures or shortcomings.
Today, civilized society tends to prefer man-made materials, mostly because we have become a society of specialists. We no longer depend on our neighbors to help us raise the barn, we just hire an architect and builder and write checks to cover construction expenses. And, in doing so, we tend to try to go with the easiest and least expensive building systems. Craftsmanship has given way to volume production efficiencies. But there are still natural homes being built, and again, these types of construction tend to use the most perfect green products, with low embodied energy and impact on indoor air quality (IAQ).
There are a wide variety of natural building systems in use in construction today, including straw bale, rammed earth, cob, cord-wood and adobe, each with recognizable benefits. It is up to you to research their suitability for your climate, as well as verify actual thermal performance and other benefits. There are entire books on each of these building systems, so we recommend that you do your own research into any specific type that you are considering. Energy modeling can assist you with this, but you should seek out qualified local referrals from those who have used and are experienced with each type of building system you are considering. Our goal is just to make certain you are aware of them and to encourage you to consider these alternative choices to wood-framed construction.
No book on green building would be complete without recognizing the passive strategy offered by earth-sheltered construction. Raw materials from the earth are the most abundant building materials available, and, if locally sourced, should have the best life cycle assessment. Using the earth’s ability to act as thermal mass helps to mitigate heat transfer in climates with high diurnal swings. There are, of course, other considerations that must be addressed, primarily fresh air ventilation, daylighting and moisture control. Whether you are considering above-ground earth-bermed construction, below grade (or built into a hillside), or living in a cave, each has its own structural challenges and requires expert guidance to assure safety and durability.
- Alternative Building Systems:
Alternative building materials markets are dominated by structural insulated panels (SIPS), autoclaved aerated concrete block (AACs), and insulated concrete forms (ICFs). These materials are generally considered durable, offer above average thermal performance, and generate little construction waste. Depending on the materials used to manufacture them, they may or may not contribute to indoor air quality issues. They are resistant to fire, mold and mildew, pest and weather damage, and offer good acoustic ratings. Some alternative systems, like structural insulated panels (SIPs) can be made from agriboard (straw board) and bio-based foams that have less effect on air quality. AACS also have low impact on air quality. Again, do your research beyond what the manufacturer is promoting about their performance and find a builder experienced in these materials to advise you on what is appropriate for your area.
- Pest Control for the Structure:
If you are located in an area with a moderate to high risk for termites, you will want to look at an integrated pest management (IPM)11 plan to reduce the risk of damage to your building over its lifetime. Building codes may only require that the sole plate (the bottom framing member that touches the foundation) be treated for termite resistance, but that is not enough to stop an invading swarm of termites. For a few dollars, you can go to your local pest product supply house or go online and pick up a gallon of borate spray and a two- gallon pump sprayer and spray all of the wood framing at least three feet up from the foundation.
Most termites are subterranean, meaning they will crawl under your foundation and come up into interior walls through plumbing penetrations in your floor. To stop this, there are metal mesh systems on the market that can be installed around penetrations to cut off this point of entry. Your mason should install a fine stainless steel mesh or steel wool in your weep holes on masonry walls to negate this point of entry into wall assemblies for any pests. Some very fine sand types (16 grit) can also be used around plumbing drains and such to prevent termite entry. Other species of termites can fly, so if you have a vented attic system, make certain all exterior vents are covered by a screen to prevent entry.
- Insulation:
What is most important is thermal value, with impact on indoor air quality second. For superior thermal performance, installation quality is as important as the product that you choose. Insulation is made of materials that are bound together with thousands of tiny air gaps in the material itself, and these air spaces are what mitigate heat transfer. If the material is compressed, those little air pockets close up, or if it does not totally fill the cavity it is installed in, leaving gaps and voids, it quickly loses its ability to perform as intended.
To minimize the impact on indoor air quality, choose insulation made from materials that minimize off-gassing of volatile organic compounds (VOCs). Although the way fiberglass insulation is manufactured creates some urea-formaldehyde in the products, many fiberglass insulations contain added formaldehyde in the form of a binder to hold the fibers together. You should avoid these products with added urea- formaldehyde, as this is a toxin that can off-gas for years.
Properly installed spray foam products may off-gas most of their toxic fumes in the first 48 hours or within two weeks of installation, but a few people with multiple chemical sensitivities may still notice adverse effects for much longer periods. For these people, great care must be taken in the selection of every material used in the construction of the home and expert guidance is advised. Once you’ve addressed the thermal performance and lower impact on IAQ, then if you’ve found a product made with recycled content, consider that a bonus.
To determine thermal performance, the ENERGY STAR for homes program grades insulation installation quality in terms of Grade I, II, and III. Grade III is what we typically see with batt insulation, defined as having more than ten percent overall gaps, voids and compressions. Remember, each wall cavity may have bracing, windows, doors or other framing that makes it a non-standard sized opening. Batt insulation, on the other hand, comes in standard sizes. So, they are either cut to fit (and usually not very exactly) or they are crammed into a smaller space than they were intended to fit. The former can result in gaps and the latter in compressions. These defects in installation quality reduce your effective R-value by at least 42 percent, according to studies13 conducted at the Oak Ridge National Laboratory by Dr. Jeff Christian and Jan Kosny.
Batt insulation is also difficult to install without compressing it behind wiring and plumbing runs through the cavities, and it is not easy to cut to fit well around electrical outlet and switch boxes without compressing it. Installers are generally paid by the job so they try to do as many homes a week as they can. To make installations go faster, they will try to compress the insulation behind the obstructions and often don’t take the time to cut carefully. Then there are the gaps and compressions in cavities that are so small the installer cannot get his hand in for a proper fit. If you insist on getting a good installation of batt insulation, your contractor might be able to achieve a Grade II. This is defined by ENERGY STAR as less than ten percent but more than two percent overall gaps, voids and compressions. It is almost impossible to get to Grade I with batt insulation, as this is defined as less than two percent overall gaps, voids and compressions. Less than two percent overall represents a near-perfect installation.
Trust us, you are not going to get that kind of quality unless you are dealing with an extremely reputable firm, one that knows that you have hired an independent third-party inspector to review the quality of their work. Otherwise you have to specify this in your insulation specification or in that contractor’s scope of work agreement. Your best bet is to go with a densely packed blown-in-blanket (BIB) system, a damp spray cellulose, a rigid foam board, a spray-in-place formaldehyde-free fiberglass or a spray-in-place foam. These systems give a total fill to each cavity, and are dense enough to resist air movement and convection loops.
Batt insulation can be made from fiberglass (silica) or natural insulation materials like recycled blue jeans or cotton fibers. BIB systems use a fabric shield, stapled to the cavity studs, filled with some type of blown-in insulation material. Better choices in these include cellulose (recycled newspaper treated with borates, which is preferred, or aluminum sulfate added for termite resistance and fireproofing), rock wool or formaldehyde-free blown-in fiberglass.
Both open-cell and closed-cell spray foam insulation products are also total fill systems. Some foam products have a small percentage of bio- based content made from natural, living materials, such as soy-based foams. Foam products act as their own air barrier, so you can expect the best overall performance from this type of insulation.
When using spray foam for sealed attics, your choice in products should depend on your climate type. Spray foam insulations are defined by the type of cell formed by the foam and by the density per cubic foot. If you live in a hot/humid, hot/dry or mixed-humid climate you can use either open-cell one-half-pound density or closed-cell two-pound density spray foam. If you live in a cold or severe cold climate, you must use only the closed-cell foams for its low water vapor permeability to avoid problems with condensation in the winter.
The difference between the two products is their permeability to water vapor. Open-cell foam is far more vapor permeable at 5-7 perms than closed-cell foams that are less than one perm. This is not a problem in warm or moderate climates, but very cold climates require a vapor barrier or vapor retarder to prevent condensation of cold winter surfaces. You can obtain a free copy of a White Paper titled “Proper Design of HVAC Systems for Spray Foam Homes” covering all aspects of building a home with spray foam at bpchomeperformance.com. This report provides expert guidance for you, your builder and your HVAC contractor on equipment selection, design, ventilation, duct design, indoor air quality, moisture control and other topics.
- Windows:
If we go back to the design strategies discussed in House Designs category , you’ll recall that windows serve multiple purposes. This means using different styles and ratings of windows for different sides of the home to provide passive ventilation, control the amount of solar heat gain desired, and provide daylighting and views of the outdoors that can improve our mood and contribute to our overall health. Windows usually comprise 10-25 percent of the exterior wall area of a home and generate 25-50 percent of the heating and cooling loads on the mechanical systems.
Window products themselves have come a long way in terms of thermal performance over the past fifteen years, so we now have a wide selection of high-tech glazing products available to us. Known as Low-E or low-emissivity glazing, these windows far outperform the clear glass windows of yesterday. Low-E glazing applications for cooling-dominated climates are tuned to reject solar heat gain, thus keeping the home cooler while allowing visible light to enter. They do this by selectively filtering out the invisible, but heat-rich, infrared part of the spectrum. Different low-E glazing applications for heating-dominated climates allow solar heat to enter but then reflect it back into the home when it tries to leave again. Thus, they act much like a greenhouse glass, helping to heat the home for free. Guidance is available to help you select the best glazing products for your climate and give you insight into how much each option will save you on your annual energy bills. Enter your zip code at the US Department of Energy’s Efficient Windows Collaborative website (efficientwindows.org) and it will direct you to window specifications right for your climate and give you insight into how much each option will save you on your annual energy bills. Beyond coating options, there are numerous choices in materials and performance available, with double and triple pane that help to manage heat transfer and frames that are thermally broken metal, vinyl, fiberglass and, of course, wood and wood composites.
The National Fenestration Rating Council (NFRC) is the independent industry- and government-supported non-profit third party that tests and rates windows and doors for performance criteria. National building codes require NFRC labeling. If no NFRC product label is available, the builder must use performance values found in a default table and not those provided by the manufacturer in calculating overall building assembly code compliance. Our advice is that you do not accept any windows that are not tested and labeled by the NFRC.
- There are four ratings reflected on the NFRC window and door label:
U-factor (also known as U-value), SHGC (solar heat gain coefficient), VT (visible light transmittance) and AL (air leakage). In building performance, the first two are of primary interest, but what you are looking for may vary not only in terms of your climate, but also the location and orientation of the window on your home.
The U-value indicates the thermal conductivity of an assembly in BTUs per hour per square foot per degree of temperature difference, indicating how well the assembly insulates and prevents heat transfer. The lower the U-factor, the better its insulating value. It’s common now to find windows with U-factors from 0.27 to 0.40. However, it’s important to put that in perspective by understanding that the U-value is the inverse of the product’s R-value.
A wall assembly with an exterior cladding, air space, house wrap, insulative sheathing, structural framing, insulation and drywall may have a combined R-value of R-15. The inverse of R-15 is 0.066, which represents the wall’s U-value. Windows with a U-value of 0.20, then, have an R-value of only R-5. Even the best windows on the market still perform around three times worse than the average wall assembly, allowing far more heat flow than the same area of wall does. The more windows we put into a wall, the more we are reducing the overall energy performance and comfort that wall delivers. Smaller, fewer and better windows pay off in terms of improved overall building performance, comfort, durability and efficient operations. Remember, designs that strategically place windows for utility, not just as aesthetic embellishments, result in smaller mechanical systems, thereby lowering our initial costs of both windows and HVAC, as well as our operational costs over time.
The Solar Heat Gain Coefficient (SHGC) measures how well the window blocks the sun’s radiant heat. Since the SHGC is the percentage of solar heat that comes through, the lower a window’s solar heat gain coefficient, the less solar heat it transmits into the house. In a hot climate, you want to reduce solar heat gain, while in colder climates you will want to maximize it. In general, southern builders will try to attain the lowest possible SHGC. Builders in the north are generally more interested in windows that insulate best and select the lowest possible U-factor. In other words, in the south you want to keep the sun’s heat out, while in the north you want to let the sun’s free heat in and keep the cold out. If the window is located on a wall where you want solar heat gain in the winter, you may not want a low SHGC rating. In passive solar strategies, windows located on the south side of the house can be protected by overhangs that shade the glass from radiant gain in the summer, but allow that gain in the winter when the sun is lower on the horizon. When using this strategy, you would select a higher SHGC for your solar collection windows to let the heat in. On the north side of the house, there is never direct radiant gain on these windows, so this rating is not as important.
Visible Transmittance (VT) measures how much light comes through a window product. VT is expressed as a number between 0 and 1. The higher the VT, the more light is transmitted through the glass and the brighter your rooms will be. Air Leakage (AL) is indicated by an air leakage rating of the window assembly, expressed as the equivalent of the number of cubic feet of air passing through a square foot of window area when under a given test pressure (cfm/square feet). The lower the AL, the less air will pass through cracks in the window frame.
Windows come in a number of operable styles, including single-hung and double-hung windows, horizontal windows (sliders), casements, louvers and awnings. A good green architect should specify window types for each location in the home to first maximize their particular benefits and then determine how those windows fit into the aesthetic architectural design.
Transom and clerestory windows can be fixed or operable and provide daylighting when installed high on exterior walls or in a cupola or monitor. When operable, they also serve to exhaust rising warm air, as an integral component in a stack ventilation strategy. Double-hung windows (both the lower and upper window sashes can be opened) give you the benefit of cross-ventilation without compromising security. Single-hung windows (only the bottom window sash can be opened) and horizontal sliders (one panel slides either left or right instead of up or down) are less expensive, and can be mixed and matched to serve various room configurations. Casements crank open and closed with the glass panes opening vertically, or rotating sideways either to the outside or to the inside. So if you plan them to crank open in the direction that the prevailing breeze is flowing, these function well to capture and direct that breeze into the living space. Hoppers and awning windows work well in basements and can provide ventilation when used over interior doorways. Awning windows crank open with the glass panes raising and lowering horizontally. This works exceptionally well to minimize water intrusion in case it rains while the windows are open. Casement and hopper window units often have a higher air leakage rate due to the large number of edges that must be sealed to make them tight, while sliding window types have a higher failure rate over time as their gaskets wear out. Check and compare their air leakage rate on the NFRC label to know for sure.
Which materials the windows are made from is a matter of your budget and personal preference. Fiberglass and wood-clad windows are a good choice, if you can afford them, as they are very durable, have long life expectancy and are repairable. Vinyl windows are readily available and dominate the window replacement market. Metal windows should only be considered if they have a thermal break, meaning there is an air space or insulation filling a gap between the inside and outside of the frame, reducing heat transfer. New phase change technologies are making it possible to develop windows that can darken to provide privacy when needed and lighten to increase daylighting. Other technologies may allow windows and other wall and even roof assemblies to reflect or absorb solar radiant heat, as desired for different climates, seasons or times of day, or to act as solar collectors (building-integrated solar photovoltaic). These and other smart home technologies are expected to be on the market within this decade. The future is near!
- Roofing:
The most important functions of your roof are to provide shelter for your structure and to contribute to optimizing the building’s thermal performance. Shelter is more a function of design and installation quality, so it is important to make sure that your roofing contractor uses good-quality flashing materials and methods. Remember, water runs downhill, so all roofing materials, including flashings, should be installed in shingle fashion, overlapping top pieces over bottom ones.
In selecting roofing materials, first go for durability and then think about how you can use the material to impact heat gains or losses, depending on your climate. If you live in a cold climate, you may want a dark-colored roof in order to capture the sun’s warmth in the winter. In hot climates, you’ll want the opposite and should select materials that are able to reflect back the sun’s heat and release any absorbed heat quickly. An independent third party, the Cool Roof Rating Council (CRRC), provides testing and reporting of roofing materials, but does not provide any certification or guidance for recommending materials. ENERGY STAR, on the other hand, does certify and label products according to their SRI (solar reflectivity index) and emissivity ratings.
Historically, white and bright metal roofs have the lowest SRI ratings and dark-colored asphalt shingles (or black tar roofs) have the highest. However, there are new pigments on the market that are coated to be able to reflect sunlight, thereby reducing heat absorption. It is important to look for the ENERGY STAR label for guidance on which roofing materials offer the best rated performance. Not only do dark colors add to the heat load of the home, they also contribute to localized temperature change — the urban heat island effect. As well, the greater the slope of the roof, the more the material contributes to this effect.
In hot climates, ventilating the roof assembly or using a radiant barrier can also reduce the amount of heat conducted through to the living space. This can be accomplished by using furring strips on top of the roof decking, allowing for ventilation under metal roofing. This eliminates condensation concerns and reduces thermal bridging through the roof assembly.
Metal and tile roof products are extremely durable with long life expectancies. If you are considering metal, make certain it is heavy gauge, and if you can afford it, chose a standing seam or concealed fastener system over a screw-down type. Every screw that penetrates your roof decking is a future source of roof leaks, and over time the screws will loosen as the metal expands and contracts with temperature changes. Tile roofs have a long life expectancy.
Tornados, hurricanes or just strong storm winds can do major roof damage. The type of roofing materials you select initially can determine how often you must repair or replace your roof, even if it is only due to normal wear and tear. Metal may seem out of your budget, but if you think that the typical lifespan of a metal roof is three times that of shingles, it is only nominally more expensive. The average composition roof shingle might last 15 years with no major risk events, but you would be considered lucky to go 30 years without an event that is considered a typical risk for your area. So, over the course of 30 years, it would not be unreasonable to have to replace that shingle roof at least two or three times if risk events occur. On the other hand, you could have installed a metal roof that would have survived all of the events of that period and still be providing a durable shield for the building for years to come. Many home insurance firms offer a reduction in annual premiums for metal roofs since they don’t need to be replaced with every hail storm and they resist fire. Metal is also infinitely recyclable, so even at the end of its life, it has salvage value.
Another aspect to consider is how the roof rafters are attached to the house. There have been several instances after tornados and hurricanes where a few homes remain almost fully intact in the middle of complete devastation in the surrounding neighborhood. Investigation into the construction methods used in these homes revealed that they shared one key construction detail: the roof rafters were attached to the top plate of the walls with metal reinforcement made for that purpose. Subsequent research has shown that if you can keep the roof on the house, the walls can withstand tremendous wind loads, but once the roof goes, the walls are doomed to fall in. If you are building in an area where tornados or hurricane-like winds occur, it would be wise and a fairly low-cost option to use reinforcing clips, straps or brackets. Hurricane ties can also reduce your insurance costs by as much as 30 percent a year in many places.
You should also think about the best type of roof if you plan to install a solar photovoltaic system for onsite power generation. You want a roof that will stand the test of time, as each time you must replace the roof you will also have to remove the solar system and all of its support structure and replace them after the new roof is installed. That can get quite expensive, and probably will not be covered by your homeowner’s insurance if the roof replacement is due to storm damage.
Of course, a very green alternative is a living green roof. This type of structure has been used for centuries around the globe, but has only recently seen some resurgence in interest, as we continue to embrace passive strategies in order to reduce our dependence on mechanical systems. Designed correctly and installed with a good membrane and the appropriate planting medium and plant species for your climate, these systems act as insulation, providing excellent thermal performance. They also mitigate the overall impact on the home’s footprint for stormwater management, carbon sequestration and heat island effect.
