I’m doing a post today from a Custom Builder Council meeting at the Austin HBA. The speakers are Peter Pfeiffer – Architect w Barley & Pfeiffer Architects and Kristof Irwin – Positive Energy.
-90% of the opportunities to build “green” occur in the first 10% of the design process.
– Example: Detached garages – keep pollutants out of the your house by making a carport
-IAQ – Indoor Air Quality. Traditional approach to dilute the toxins, what if we put less pollutants in to begin with?
-Example: Cup with a small amount of coffee in the bottom, dilute this with clean water and the cup is still murky.
-HVAC: put a few thousand more into good ducts and infrastructure LONG before going to a Geothermal system.
-HVAC: Take your duct leaking % and multiply by 4x and that’s your system’s % IN-efficiency.
-Example: An HVAC system with 10% loss is really about 40% less efficient than it should be
-Broad overhangs are your friend in this climate. Consider using a raincoat vs an umbrella. You could be naked under a golf umbrella and not get wet. Bigger overhangs are the friend of long lasting buildings.
-Base Flashing- The first 2′ up from the foundation needs a super good raincoat. Use a sheet rubberized base flashing around the perimeter of the foundation. Houses get killed with water at the base over the years especially here in TX with our sprinkler systems going off at 4AM. The bottom few feet of houses take a rainstorm beating by sprinkles multiple times per week. This base flashing is critical!
Humidity Control: Starts at the source. Bath and Kitchen exhaust fans are a must. Use a high quality fan with a Timer so they will be used EVERY time.
-Be careful with high draw pro exhaust range fans. Most of the time these are overkill
Ducting. You get 2x the air movement from the same wattage using smooth metal vs flex ducting.
Photo of 15 year old deteriorated Flex Duct. Flex has 1/3 to 1/4rd the life span of Metal ducts.
-Duct leakage is huge in our climate. This is why you must put all your ducts in the HVAC space of the house. When ducts are in the hot/unconditioned attic they leak air outside the house and that puts your house in a negative air situation. They push air out of your house and the air is made up by leaking back unconditioned/hot/humid air in from attic registers/doors/windows/etc.
-Big believer in UV lights to keep mold from growing inside the HVAC system ducts.
-Shoot for 5% loss or less in your Duct Blast tests.
Barometric Damper. www.fieldcontrols.com MAS-1 $50 and this damper only opens with the house goes negative. It’ll only bring in outside air when it’s needed.
-Build the house TIGHT. You can’t ac the whole neighborhood.
-Control pollutants at the source. Including Front Loader washers so you’ll get less soapy humid air released.
-Bring ALL your ducts into the conditioned space of your house.
Question: How many of the audience had Air Conditioning growing up? (1/3rd of the hands go up)
Question: How many of you have AC today? (all hands up)
Wind effects: The wind exerts extreme pressures on your house.
-Example: Take an empty coke can and point it into the wind. Once the can is full of air, none will move through it. On the other hand drill a small hole in the can and you’ll move tons of air through it as it’s pointed into the wind. This is an example of why we build TIGHT houses.
Traditionally insulated attics with insulation at the ceiling level. Hot air expands and when your attic is hot that expanded air is pushing its way through your holes in the ceiling plane to get in your house.
A phone booth contains about 1 lb of air. Multiply this by the CFM’s moving through your furnace and…A 3 ton furnace fan will move over 20 tons of air through the system in the course of 24 hours. This is why your furnace uses SO much energy.
-Fan cyclers to open the damper for fresh air are not a good idea anymore. They bring in too much air and they aren’t “smart” to know when people are home. Use a Field Controls MAS-1 barometric damper and only bring air when the house goes negative.
-The more sophisticated the more prone to breakage. Example: Humidity sensor bath exhaust fans are pretty techy and could break in 5-10-15 years. Use a good fan with a simple countdown timer.
-There is talk that by 2015-2018 all houses in City of Austin would require ducts to be in conditioned space of the house.
1 Ton of AC = 12,000 BTU capacity. The smallest standard AC system you can buy is 1.5 Tons. So, this is why mini-splits are called “mini”. They come in .5 Ton increments.
Variable Refrigerant Flow – This is the future of AC units. Mitsubishi has been making these for years. Most AC condensers are one speed.
Example: Consider if your car was ONE speed. You only had on/off. No gas pedal, you could only use the key to start or stop. You car ran OFF or FLOORED 100% speed. That would be a terrible car.
Same with your AC unit. Most AC’s are running 100% ON or TOTALLY OFF. These Variable Speed Compressors can run 15% up to 115% and anywhere in between. Consider a 3 ton system. It has 36,000 BTU capacity and if it’s a single speed (sometimes called one stage) then much of the year it’s cycling off/on a bunch to try to control the temp in your house. Just like a 1 speed car it’s very inefficient. Stopping starting all the time.
Mitsubishi City Multi – S series is a variable refrigerant flow system that is DUCTED and looks like a standard HVAC system. It runs 20+ SEER and is super efficient. (look for a future blog post on this from me as I’m about to install one)