Watch Frank use a thermal imaging camera to compare how much cold air is coming in through two glass block windows (the darker the purple color - the more cold is coming in). One built with mortar, the other built with silicone.
Mortar Versus Silicone:
~Frequently Asked Questions About Glass Block Windows~
Q: Why do you assemble your glass block windows with silicone? Isn’t mortar the industry standard?
A: Yes, mortar is the industry standard—of a century ago, before the development of silicone. Mortar is a natural conduit for cold, making mortar-built glass block less energy efficient than silicone-built ones. Fact is, the manufacturers of per-assembled glass block windows for the construction industry and the big home improvement stores use glass block silicone, not mortar. That’s today’s industry standard.
Q: Doesn’t Minnesota Building Code specify mortar for glass block windows?
A: Minnesota Building Code specifies mortar for the INSTALLATION of the glass block window—where the perimeter of the window meets the foundation opening. It does not specify the material that bonds the glass blocks. Of the many thousands of glass block windows we’ve installed, we've never had one that did not pass inspection.
Q: I want glass block windows for security. Wouldn’t it be easy for a burglar to cut through silicone with a utility knife?
A: Utility knives have a blade perhaps 3/4 inch long. Glass block windows are three to four inches thick. Besides, the silicone is really tough and hard to cut. Silicone is resilient whereas mortar, while strong, is brittle. It doesn’t flex and once it has cracked its integrity is compromised. We've replaced many of our competitors glass block windows, some made with silicone and the vast majority made with mortar. The silicone windows are much harder to remove than the mortared ones. Once the mortar window cracks they are easy to remove, but realistically both mortar and silicone glass block windows are a deterrent to an intruder.
Q: What about mold and mildew?
A: The silicone adhesive contains anti-microbial and anti-fungal additives that prevent mold and mildew growth. Mortar, unlike silicone, is porous and can absorb and retain water, making it an inviting host for mold and mildew.
Q: Which lasts longer, mortar or silicone?
A: The glass block silicone that we use is manufactured by the largest glass block manufacturer in the world. It doesn't crack and it has a 20 year manufacturers warranty. Mortar can crack in a matter of weeks.
Mortar cracks! Silicone flexes.
Basement walls move, they are subject to temperature extremes. There is expansion and contraction, settling, and lateral pressure from water and frost heave. This is what causes the mortar to crack, sometimes as soon as a few weeks after installation. Because of this, mortar is not the best choice for basement walls. Silicone is the best choice for basement walls because it can flex. It does not crack!
Q: Which is the most energy efficient, mortar or silicone?
A: Years ago Pittsburgh Corning (which is no longer in the glass block business) had a fenestration test done on a mortar assembled glass block window, just like the mortared window in the video above. The result was a U-factor of 0.57, on a silicone assembled glass block window a fenestration test revealed a U-factor of 0.51. U-factor, or U-value, is the measurement of a windows ability to keep the cold outside and the heat or warmth inside. U-factor in the window industry is what mpg (miles per gallon) is to the automobile industry. U-factor gives consumers a way to compare a windows energy efficiency. The lower the U-factor number, the more energy efficient the window is. One of the reasons we use silicone is it insulates better than mortar, as the fenestration tests proved! Silicone built windows are warmer than mortar built windows. Mortar has almost zero insulating value, and when the mortar cracks it has even less ability to keep out cold air, ants, bugs, spiders, and any other creepy crawlers. In addition to building our windows with silicone we put insulation in between each and every individual piece of glass block, when we assemble your window. We are the only company that we know of that takes this extra step. We feel our glass block windows, because we have insulation in every single joint, and because of the silicone we have to hold those joints together, are about 20% more energy efficient than a mortared glass block window. The thermal imaging camera in the video confirms our insulated glass block window is more energy efficient.
A: Yes, mortar is the industry standard—of a century ago, before the development of silicone. Mortar is a natural conduit for cold, making mortar-built glass block less energy efficient than silicone-built ones. Fact is, the manufacturers of per-assembled glass block windows for the construction industry and the big home improvement stores use glass block silicone, not mortar. That’s today’s industry standard.
Q: Doesn’t Minnesota Building Code specify mortar for glass block windows?
A: Minnesota Building Code specifies mortar for the INSTALLATION of the glass block window—where the perimeter of the window meets the foundation opening. It does not specify the material that bonds the glass blocks. Of the many thousands of glass block windows we’ve installed, we've never had one that did not pass inspection.
Q: I want glass block windows for security. Wouldn’t it be easy for a burglar to cut through silicone with a utility knife?
A: Utility knives have a blade perhaps 3/4 inch long. Glass block windows are three to four inches thick. Besides, the silicone is really tough and hard to cut. Silicone is resilient whereas mortar, while strong, is brittle. It doesn’t flex and once it has cracked its integrity is compromised. We've replaced many of our competitors glass block windows, some made with silicone and the vast majority made with mortar. The silicone windows are much harder to remove than the mortared ones. Once the mortar window cracks they are easy to remove, but realistically both mortar and silicone glass block windows are a deterrent to an intruder.
Q: What about mold and mildew?
A: The silicone adhesive contains anti-microbial and anti-fungal additives that prevent mold and mildew growth. Mortar, unlike silicone, is porous and can absorb and retain water, making it an inviting host for mold and mildew.
Q: Which lasts longer, mortar or silicone?
A: The glass block silicone that we use is manufactured by the largest glass block manufacturer in the world. It doesn't crack and it has a 20 year manufacturers warranty. Mortar can crack in a matter of weeks.
Mortar cracks! Silicone flexes.
Basement walls move, they are subject to temperature extremes. There is expansion and contraction, settling, and lateral pressure from water and frost heave. This is what causes the mortar to crack, sometimes as soon as a few weeks after installation. Because of this, mortar is not the best choice for basement walls. Silicone is the best choice for basement walls because it can flex. It does not crack!
Q: Which is the most energy efficient, mortar or silicone?
A: Years ago Pittsburgh Corning (which is no longer in the glass block business) had a fenestration test done on a mortar assembled glass block window, just like the mortared window in the video above. The result was a U-factor of 0.57, on a silicone assembled glass block window a fenestration test revealed a U-factor of 0.51. U-factor, or U-value, is the measurement of a windows ability to keep the cold outside and the heat or warmth inside. U-factor in the window industry is what mpg (miles per gallon) is to the automobile industry. U-factor gives consumers a way to compare a windows energy efficiency. The lower the U-factor number, the more energy efficient the window is. One of the reasons we use silicone is it insulates better than mortar, as the fenestration tests proved! Silicone built windows are warmer than mortar built windows. Mortar has almost zero insulating value, and when the mortar cracks it has even less ability to keep out cold air, ants, bugs, spiders, and any other creepy crawlers. In addition to building our windows with silicone we put insulation in between each and every individual piece of glass block, when we assemble your window. We are the only company that we know of that takes this extra step. We feel our glass block windows, because we have insulation in every single joint, and because of the silicone we have to hold those joints together, are about 20% more energy efficient than a mortared glass block window. The thermal imaging camera in the video confirms our insulated glass block window is more energy efficient.