Archive for the ‘Building Systems & Methods’ Category
Exterior Insulation on Masonry Substrates
Friday, September 23rd, 2011I’d like to thank Toronto Stucco Contractor Skylar Bowker for the following guest post on the benefits of applying exterior insulation to existing masonry buildings and/or masonry substrates.
Recent studies have brought to light the advantage of exterior insulation versus traditional between-the-stud insulation. Among them: the ability for insulation to be continuous (instead of broken at studs), the superior longevity of rigid insulation versus fibreglass (which becomes less effective over time) and dew-point management. But how do you adhere rigid insulation to masonry substrates? Are you out of luck if you have brick? Isn’t drilling into masonry into time consuming and cost prohibitive compared to other cladding solutions? Not with adhesive.
Insulation can be installed on masonry substrates using adhesives because of the light weight of rigid insulations such as expanded polystyrene (EPS) or extruded polystyrene (XPS). The best solution for adhering insulation to a masonry substrate is actually a cement-based adhesive, such as one offered by an EIFS manufacturer (Dryvit, Sto, Senergy). These adhesives are Portland-cement based, but are modified with an acrylic component as well as fiberglass-mesh fibers that allow the cement to expand and contract with the insulation without cracking. This ensures that the rigid insulation maintains a strong bond to the masonry substrate for decades longer than traditional cement and doesn’t delaminate.
Additionally, because the insulation is being installed over a cementitious substrate a weather barrier isn’t typically required. While a cementitious-weather-barrier will never hurt, it does add to the cost and may be unnecessary. If the masonry substrate is crumbling or coming apart however, loose pieces should be removed and a skim coat should be applied to prevent further decay.
Anyone familiar with EIFS will know of the problems of incorrectly applying the cement adhesive to the back of the insulation boards. In order to prevent moisture from becoming trapped, the modified-cement adhesive must be installed in vertical “ribbons”. Using a 1/2”x1/2” notched trowel with 2” spacing between notches, apply the ribbons in a vertical fashion, which will allow water to drain vertically once installed on the wall. The insulation boards should be installed in sheets no larger than 24”x48”, laid lengthwise, and staggered. Sufficient pressure needs to be uniformly applied to the insulation boards so that the adhesive is pressed into the wall, but not so much as to flatten the ribbons and close up the drainage channels.
Is EPS or XPS better? The answer depends on your needs. If cost is a restriction, EPS is likely the better solution with its lower costs. If space is a constraint (as is common with closely-built downtown homes), the higher density of XPS will provide an equivalent R-value with less thickness, albeit at a higher cost. For example:
- EPS
is R=3.75/inch (2.5” for R-9) - XPS
is R=5.6/inch (1.5” for R-8.4)
Nearly identical R-values, but the EPS is 1” thicker than the XPS. Note that EPS and XPS can have varying densities, which will affect the R-value per inch. While having “geometrically defined drainage cavities” (grooves cut into the back) is preferred for additional drainage, it’s not absolutely required. For more information on r-values, see http://en.wikipedia.org/wiki/R-value_(insulation)
There are a few systems/claddings available over the installed exterior rigid insulation boards. By far the most common is Exterior Insulation Finish Systems (EIFS, sometimes called “synthetic stucco”). To finish off an EIFS installation, alkali-resistant fiberglass mesh must be embedded into the EIFS base coat, and a finish coat applied at the very end. Various details such as control joints, proper termination at grade, flashing above wall penetrations and more need to be addressed, and as such a skilled EIFS applicator is usually recommended. A full detailed explanation is beyond the scope of this guide, but manufacturer guidelines can be found online or at distribution centers.
Heavier materials such as stone veneer, traditional stucco and brick veneer require a metal lath and possible extra reinforcing. This is beyond the scope of this guide, and the respective suppliers should be contacted for exact installation details.
Another alternative is foam-backed vinyl, which doesn’t have nearly as nice of a finish as EIFS but is more forgiving in terms of installation and can be installed/purchased at a lower cost. Vinyl siding manufacturers may or may not support the above specified installation process with a cementitious adhesive, and the manufacturer must be contacted for warranty information as well as their own installation methods.
There you have it. With the use of the proper cement adhesive, rigid insulation boards (EPS or XPS) can be installed directly over masonry substrates without the need to drill into walls. Not having a piece of metal sticking through the insulation also avoids thermal bridging, making your building as energy efficient as possible. Home owners, general contractors or architects in the Toronto area are invited to visit Toronto Stucco Contractor and contact Skylar Bowker to get a quote on having their new or existing building fitted with Exterior Insulation Finish systems.
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VIDEO: What is a LEED Home? Watch!
Friday, November 13th, 2009
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Prefab Houses Bomb
Wednesday, July 1st, 2009Remember the big push for prefabs? There have been several iterations of the “Structural Insulated Panel” idea. Then there was the house delivered prebuilt on several trucks. All you had to do was plop it down on your foundation, hook up the utilities and sewer, and you were done.
Great idea, right? Well… Not so much. Despite the entrance of famed architect Daniel Libeskind into the prebuilt fray, Build LLC is declaring the whole prefab fling dead.
Read the whole article and their 10 reasons why: here.
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Understanding The Alternatives
Saturday, April 25th, 2009While there are plenty of inexpensive ways to save energy in homes and businesses, the coming of the Obama administration seems to have piqued interest in alternative power. Tax benefits and rebates from power companies are sprouting up all over the country.
In California, for instance, public utilities are required to purchase power back from customers. This is called a “grid-tie” system. Businesses sell all the power they generate to the power company and then buy their power back as per normal, ensure a steady flow of reliable electricity. If properly designed, the alternative generation system can be a money maker for the company. Consumers, on the other hand, get offsets for power generated. Generation surpluses are carried forward to offset future deficits. A properly designed system can reduce a home’s utility bill by 90% or more.
Financial incentives for alternative energy generation
Beyond just the straight reduction in utility bills, there are a number of programs available to help offset the cost of installing an alternative power system. While these programs are changing all the time, here’s a short list:
- Database of State Incentives for Renewables & Efficiency (DSIRE) is a “comprehensive source of information on state, local, utility, and selected federal incentives that promote renewable energy”: (www.dsireusa.org)
- U.S. Dept. of Agriculture’s 2002 Farm Bill Initiative—”Renewable Energy & Energy Efficiency Program” provides information on USDA grants “available for eligible agricultural producers and rural small businesses to purchase renewable energy systems and make energy improvements”: www.rurdev.usda.gov/rd/farmbill/9006resources.html
- California Energy Commission (CEC): Emerging Renewables Program Rebates: www.consumerenergycenter.org/erprebate/index.html
- NYSERDA Rebate Program: www.powernaturally.org/Programs/Wind/Installers_all.asp?i=8
- The Energy Trust of Oregon is an organization funded by “Public Purpose Funds” which supports Oregon renewable energy and energy efficiency projects through grants: www.energytrust.org/RR/wind/index.html
In California specifically there is also:
- The Net Metering program
- The Feed-In Tariff
- In San Bernardino County, the Green Building Incentive
- In Santa Monica, the Green Building Grant Program
- And the Self-Generation incentive Program
And Federally there are also the:
- Residential renewable Energy Tax Credit
- Business Energy Tax Credit
It’s Cool But Not Cheap
As with all things new and or in vogue, alternative energy is still not cheap. Well designed systems start at $10-$12 per watt and go up from there, depending on individual choices for generation systems, additional systems desired (such as battery backup or completely “off-grid” systems) and so on. Home owners can expect their new alternative power system to pay for itself in 10-15 years, depending on local utility costs.
A business system can take significantly longer depending on the size of the system and how it is used. This is because, in California anyway, businesses must sell their power to the utility company at wholesale rates, which is about half of what they pay to purchase that power back.
Solar
The best known alternative source of power is, of course solar. It’s the great granddaddy of alternative energy and has long been the darling of alternative energy enthusiasts. Things have changed since the early days of solar power. Now not only are the familiar crystalline panels more efficient than ever before, solar roofing systems are also available. Some of them don’t even look like solar panels!
As with all alternative power systems, there are many do-it-yourself kits out there for those who are handy. But the best systems are always professionally designed for the specific application and location.
Wind
Small scale wind power is the new kid on the block. As such, it’s poorly understood. Companies are sprouting up all over the place touting their product’s abilities, taking advantage of consumer ignorance.
Wind energy functions on a very simple principle of physics: The amount of wind a turbine can generate is equal to the cube of the wind speed. Therefore the holy grail of wind turbines is rotor size. (Laymen refer to the “rotor” as the “blades”.) The larger the rotor—or more accurately, the more surface area available to catch the wind—the less wind it takes to generate a given amount of power. It’s that simple. It’s also why commercial wind turbines are well over a hundred feet tall with rotors a hundred feet in diameter. The power company wants maximum power generation at the average (or “rated”) wind speed for the locale.
So don’t be fooled by manufacturers touting the energy output potential of their products. You’ll never hear an expert in wind energy talk about a turbine’s power “size”. What you’ll here them discuss—at length—is it’s rated power at its rated wind speed. In other words, how much power the turbine will produce at the speed the wind blows most of the time at that location.
Of course, there are many different ways to increase surface area on a turbine, and all seem work equally well.
Consider the turbine show at right. While the manufacturer didn’t have a spec sheet available at the time this was written, according to the faq, at a speed of 28 mph this turbine produces half its rated power of 10kw. And at 14 mph, it outputs 2kw. Not significantly lower than the 2.4kw produced by the more traditional tower shown above with it’s 12 foot rotor.
The Ideal System
Beauty, they say, is in the eye of the beholder. Likewise with alternative energy. Wind offers a viable (though no cheaper) alternative to solar power in some parts of the country. In many places, combining the two would provide all the energy needs of a home or business, making an off-grid option fully viable.
Personally, I think a combined wind/solar system with a grid-tie and a battery backup is the idea system. If the worst happens, the grid is still there, but by in large, the property is energy independent.
There’s no doubt in my mind that not only are are alternative energy sources here to stay, in another couple of decades they may well make up a significant portion of our national power grid! I sincerely hope so!
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