Filed under: Enclosure, Materials and Methods, Structure | Tags: SIP, Structure
The concept of structural insulated panels is simple; create a load bearing wall panel that is also made of an insulating material. Recently, I’ve heard a good bit about Kama panels. They won an award for being one of the top green building products of 2009. I also noticed that Kama panels were central to the design of this green home to be built by a Popular Science staff member. Traditionally the panels have consisted of rigid foam insulation sandwiched between two layers of OSB plywood. However, the Kama panels are unique in that they eliminate the OSB and utilize polystyrene insulation sandwiched by metal studs. The panels can be used as walls, floors and roofs. The factory controlled assembly claims to save time, money and labor on-site. The Structural Insulated Panel Association says the core insulation is 98% air and does not rely on CFC’s. I’m looking forward following the performance of these systems over time. It certainly feels lego-like to imagine quickly tilting up styrofoam walls to create a small building. If anyone has experience using these systems, please share more information in the comments.
I was told to always say sealant, not caulk. Here is a little research about what products are currently available. Caulk originated in boat making; Sealant was first used in building construction. Both products serve the same purpose: to keep water and air from getting within a joint. In construction, some manufacturers today use caulk as an all-purpose term and sealant to refer to high-performance products. In commercial construction, it’s always sealant. Here is an attempt to identify the current options for application of architectural sealants.
Sealant Failure – To better understand the selection process for sealants, first understand the common reasons for sealant failure that need to be prevented. The following failures usually happen for one of two reasons; either the substrate was not properly prepared or the wrong product was selected.
- Adhesive: bond between caulk and substrate fails
- Cohesive: the caulk itself tears
- Substrate: substrate breaks
Joint geometry - Higher performance sealants require a backer rod to create a width to depth ratio of 2 to 1.
Factors for sealant selection:
- What material is the sealant adhering to?
- How much it is likely to move?
- Will mold and mildew be present?
- Will it need to resist weathering?
- Will temperature and humidity affect the installation?
- Should it match a specific color or texture?
- Will it need to resist abrasion?
Types
- Water Based
- Latex products including acrylic and vinyl
- Apply and let cure in warm (40°F or more) and dry conditions
- Good choice for most interior applications
- Easy workability: smooth, thin consistency
- Paintable
- Adhere to most building materials
- Silicones and Polyurethanes have superior performance, but some newer water based products provided added performance.
- Spray foam – water based sealants are also available. Not for moisture resistance.
- Polyurethanes
- Difficult to apply in cold weather
- Stringy
- Toxic
- The only sealant that can stand up to traffic and abrasion.
- Expanding polyurethane foams are also available.
- Silicones
- Best choice for metal, glass, tile and cold weather
- Adheres to non-porous substrate best
- [typically] cannot be painted
- It tears. If sealant if damaged, cannot repair the existing installation.
- Adheres poorly to wood
- Handles extreme weather well.
- Remains flexible for joint movement
- Stinks, but not toxic
- Unaffected by mold and mildew
- Resists UV degradation
- Synthetic Rubber
- Most flexibe and clearest curing
- Ideal for exterior joints likely to expand and contract
- Solvent based can be applied in wet and cold weather
- Resist mold and mildew
- (Low modulus) Stretch and recover easily without breaking. Since they stretch easily, there is less likelihood that the bond with substrate will break.
- Best product for weathering exterior wood
- Paintable with water based paint
- Flammable until cured
- Do not meet VOC (volatile organic compound) regulations and should not be used indoors
- Butyls
- Very messy
- Stretch but do not recover
- Most water resistant product available
- Unattractive tar-like appearance
- Used in gutters, roof flashing & anywhere needed below grade
- Never completely hardens. can withstand movement of a shear joint
- Unclassified Hybrids
- Modified-silicone polymers
- Combine chemistry and benefits of water-base, silicone, and polyurethane
- Expensive, but high-performance
- Like latex and acrylic, they are easy to apply
- Like polyurethane, incredibly durable and adhere to most any substrate
- Like silicone, can be applied in extreme temperatures and withstand water immediately
- Flexible and paintable
References:
Exterior Building Maintenance of New York City School Buildings
Filed under: Materials and Methods, Mechanical | Tags: air tightness, blower door, mold, ventilaltion
Amongst the sea of sustainable architecture issues to discuss, an important testing procedure has not been mentioned enough in the reading I’ve encountered. The Blower Door Test helps energy auditors determine a home’s air tightness. The reasons to understand building tightness include thermal comfort, moisture control, air quality control and of course to identify energy waste due to air leakage.
How they work from the U.S. Department of Energy Efficiency and Renewable Energy:
A blower door is a powerful fan that mounts into the frame of an exterior door. The fan pulls air out of the house, lowering the air pressure inside. The higher outside air pressure then flows in through all unsealed cracks and openings. The auditors may use a smoke pencil to detect air leaks. These tests determine the air infiltration rate of a building.
I also recently read an article that asks if homes too air tight. From this article:
Probably the most widely published symptom of a tight underventilated house is condensation and moisture build-up. Condensation on windows, mold growth on cold surfaces and dust mite infestations in carpets are becoming more frequent in new houses as airtightening reduces natural ventilation rates and indoor humidity levels increase.
So it seems there is important reason for both an air tight home and a home that has adequate natural ventilation. To keep occupants comfortable, obviously, we need mechanical ventilation and a tight home that does not waste energy through air leakage. On the flip side, to avoid the behemoth of a problem that is mold and mildew, we need some natural ventilation. The article concludes with some suggestions for successful strategies:
Mechanical ventilation for your houses does not have to be complex or expensive. Something as simple as a quiet 75 CFM bathroom fan running continuously will be adequate in some houses.
Most experts agree that continuously operating, low-level ventilation that requires little occupant attention is best. Studies indicate that homeowners often turn off or permanently disable mechanical ventilation for a variety of reasons, but especially due to noise. If you choose the right system and have it properly installed, noise simply shouldn’t be a problem. The bottom line is that if homeowners can’t hear the ventilation system running, it has the best chance of being used.
Any mechanical engineers out there that can offer direction or innovative solutions on this topic?
Here is an attempt clearly identify the current options available for flat roofing systems. First off, remember the basic intention that flat roofs need to drain water by having a slight slope. Here are the types as found on the Wikipedia – Flat roof page. I’ve tried to both summarize this list and add in other information for architectural consideration. Please comment if you can provide any correction or additional information.
Coal-Tar Pitch Built Up Roof
- Byproduct of coal industry
- Heated coal tar between layers of saturated felt
- Can soften in warm temperatures and ‘heal’ itself
- Always ballasted with gravel on top
- Proven longevity
- Fumes are hazardous
- Melted in kettle on site
- Slope of 1/4″ per foot or less.
Asphalt Built Up Roof
- Currently the most common flat roof
- Multiple layers of reinforcing plies and asphalt for redundancy
- Gravel surfacing material is common
- Cracking and UV degradation are concerns
- Byproduct of oil industry
- Melted in kettle on site
- Can later repair and recoat with compatible product
- 4 Types
- Type I: used on dead level, closet to coal tar
- Type II: up to 1/4″ per foot
- Type III: up to 2″ per foot
- Type IV: ’special steep’
Turbo Seal
- Self healing gel like membrane that never cures
- Rubber (mostly used tires) infused with adhesives
- Applied to existing asphalt roof. Then cap with sheet membrane
CSPE – Chlorosulfonated Polyethylene
- Synthetic rubber roof
- Seams are ‘welded’
EPDM – Ethylene Propylene Diene Monomer
- Synthetic rubber roof
- Single ply
- Simple to apply
- When air conditioned space beneath, moisture gain can be a problem
- Does not like to adhere to itself. Seams can be a problem.
- Low cost membrane
- Three methods of installation:
- Ballasts on top of membrane
- Mechanically attached
- Fully adhered (expensive, but best performance)
Cold applied liquid membranes
- Increasing in popularity
- No flames or heat needed
- Seems to be excellent at covering intricate changes in plane
- Can anyone report on long term performance and maintenance of these products?
- Steps I observed in a recent maufacturer presentation
- Paint on layer of polyurethane
- Roll out a sheet of fiberglass reinforcement
- Upon reacting with the polyurethane, fibers ‘relax’ and become embedded.
- Paint on a second layer of polyurethane
PVC – Polyvinyl Choride
- Single ply
- Flexible
- Additives improve UV degradation
- More information on Roofingcontractor
TPO – Thermoplastic Polyolefin
- Single ply
- Seams can be heat welded
- Resistant to heat and UV degradation
- More information at National Research Council Canada
Filed under: Materials and Methods
Here is another note made while preparing for Materials and Methods exam. This can seem like a very minor thing for architects to study, but obviously any surfaces that are the final finishes that occupants touch and see are extremely important for both design and health safety. Paints are also critical in terms of sustainability.. be aware of LEED IEQ credit 4.2. Also, maybe it’s worth a look for architect’s to review the EPA’s guide to lead paint. Finally, on a cool technology note, be aware of Sherwin Williams color matching app for the iphone that matches the color of an iphone photograph to their color catalog.
Filed under: Materials and Methods
Here are a few notes about the types of glass used in construction. These are from my study for the materials and methods portion of the Architects’ Registration Exam. Just a few short notes that help me remember the various types and technologies. Please comment if you have corrections or additions.
Float Glass / Annealed Glass
- Slowly cooled on be of molten tin
Heat Strengthened
- Twice the strength of annealed
- Heated to 1100°F
Tempered
- Subject annealed glass to 1150°F, then quickly cool
- 4 times stronger than annealed
- Safety glass
Laminated Glass
- Polyvinyl Butyral Resin interlayer
- In the event of glass break, this interlayer prevents pieces from breaking completely loose and falling
Tinted or Heat Absorbing
- Reduces Solar Transmittance
- A given piece should not be half shade & half exposed. This will cause thermal stresses that could lead to breaks.
Low Iron Glass
- Reduced Iron Oxide content
- Light green cast
- Exeptional clarity
Reflective Glass
- Thin layer of metal
- Saves energy
- Reflects solar radiation
Insulating Glass
- ‘IGU’
- Hermetically sealed airspace
Patterned Glass
- Pressed through rollers
Wire Glass
- Wire embedded
- 50% stronger than annealed
Spandrel Glass
- Permanent fuse of ceramic frit color
Low-Emissivity Glass
- ‘Low-E’
- Selectively reflects and transmits certain wavelengths of electromagnetic spectrum.
- Transmits visible light & short wave radiation
- Reflects long wave heat radiation
- Low-E coating is applied to No.3 surface (see diagram here)
Other glass types
- Energy Efficient Glazing
- Electrochromic Glazing
- Fire Rated Glazing
