Air Date: 4-1-2016| Episode: 408
David Johnston is president of David Johnston & Co. He has been building custom energy efficient, healthy homes in Maine for more than 35 years…
Full Description:
David Johnston is president of David Johnston & Co. He has been building custom energy efficient, healthy homes in Maine for more than 35 years. He was building energy efficient homes with a focus on indoor air quality long before it was a mainstream thing to do. In addition to being a builder he teaches building construction trade classes at Central Maine Community College and has served as an adjunct instructor in Residential Design and Drafting and Graphic Design at the University of Southern Maine (USM). David is also currently on Advisory Committees for Southern Maine Community College, Central Maine Community College, and Westbrook Region Technology Center.
We want to discuss how a successful builder balances the sometimes competing demands of good IAQ and energy efficiency. We also want to talk about Mr. Johnston’s presentation on the Basics of Building Science at the 2016 Northeast IAQ and Energy Conference April 11-12 in Portland Maine. Radio Joe and Bob Krell from Healthy Indoors Magazine will be there doing interviews and taping a special IAQ Radio broadcast. LEARN MORE this week on IAQ Radio!
Z-Man’s Blog:
100 year homes
George Bernard Shaw wrote, “those who can, do; those who can’t, teach.” David Johnston is living proof that the old age is wrong. David is a homebuilder and college teacher
Nuggets mined from today’s episode:
Blower door testing on his home done by a team from Princeton University of .1 HCH50 was the tightest home they ever tested. Dave started building homes with double walls in 1981-82. Walls consist of 2 -2”x4” walls with 3” space in between. A membrane is installed on the inner wall. Walls are filled with dense packed blown and batted cellulose insulation or mineral wool. Has found that aligning the studs makes insulating easier. When he must use foam on renovation projects or under slabs he uses rigid.
Fortunate his clients believein what he is doing, so he encounters little sales resistance. He has previously built as many as 5-6 homes per year, he has intentionally downshifted to building 2-3 as he gets closer to retirement.
Simpler is better. Trying to keep homes small and simple is the hardest sell. The more complicated the home façade, the more leaks and less energy efficiency.
Client stated interest in energy efficiency is lip service; clients don’t really mean it and usually choose granite counter tops over better insulation.
Isn’t a big fan of foam insulation and opines that foam deteriorates and breaks down over time. He also resists installing foam on the exterior because attaching siding to thick foam is difficult. He has noticed that foam insulation is vulnerable to ant infestation.He only uses foam where it makes sense. Electricians and plumbers detest spray foam insulation because it’s hard to fish wires, pipes or otherwise penetrate. He recommends anticipating the need for future wiring by preinstalling conduit.
Heat is transferred 3 ways: radiation, conduction and convection. Heat loss via radiation is 9 watts per degree of temperature difference. David advocates that building homes with warm walls, energy efficient windows and heated floors makes for a home that is noticeably more comfortable for occupants.
Glass inherently loses heat. When there are too many windows homeowners may complain of the need to wear sunglasses indoors and of UV deterioration of furnishings and building materials. Comparing windows to the number of blades on a shaving razor, window efficiency can become a diminishing return triple glazing is the max he recommends. Low E windows help both re-radiate heat and manage UV light.
Significant energy loss occurs at joints between surfaces, especially at joint between sill plate and plywood floor.
Stuffiness complaints can be resolved with a balanced recovery ventilation system.
Uninsulated concrete floors are cold and suck heat out of occupant’s bodies. By building his way with double walls and insulated slabs, homes are comfortable and occupants wonder why?
Prefers not to build homes with attics.
Fiberglass insulation isn’t sufficiently dense to satisfy him, that’s why it gets soiled around electrical switch plates and outlets. Dense pack mineral wool or cellulose insulation is affordable, recycling and doesn’t support ant infestation.
Snow load is a big issue in New England, homes must be built able to support loads of 90 pound per sq. ft.
Old homes and barns last so long because they weren’t heated, wired or plumbed.
Ventilation was difficult in the early years (early 1980s) due to the lack of necessary accessories such as flex plastic ductwork. Today, with the available balanced ventilation equipment and accessories there is no excuse not to retrofit. He is a fan of the RenewAire Energy Recovery Ventilation systems. [www.renewaire.com]
He provides supply air to living quarters and exhausts kitchens and baths. For occupant comfort he cautions about supplying air from overhead due to convection heat loss and the importance of quiet running equipment.
When home buyer is In a budget crunch exhaust only ventilation works, you don’t know where the replacement air is coming from.
He teaches at community colleges. Construction courses are less popular now than they used to be. He is concerned that young people are receiving poor career guidance counseling and are being steered into computer science. He wonders, where the will the next generation of trades person will come from?
In Maine no contractors licensing is needed, so wannabe contractors can simply hang a magnetic sign on their truck and be in business.
Preferring that the laundry be located in the basement, he warns about the damage potential when locating the laundry on the 2nd floor.
Invites everyone to attend the: The Northeast Indoor Air Quality & Energy Conference, April 11-12, 2016
https://www.maineindoorair.org/
Today’s Music: Energy Conservation Rap by Susan Grebe YouTube
Z-Man Signing Off
Trivia Question:
What is the traditional unit of work equal to approximately 1055 joules?
Answer:
British Thermal Unit, BTU
