Zero Energy Home Construction in VT: Mushrooms in Your Carpet?

Posted by Tim Biebel on Aug 19, 2016 11:30:00 AM

You’ve decided that it’s time to downsize (or rightsize) and to do it in Vermont, so now you’re searching for a builder who specializes in high performance / zero energy home construction. You want a builder you can believe in and trust that, when it comes to High Performance construction technology, he knows his stuff.  So let’s say that have finally found a custom home builder who’s been in business for more than forty years, whose rather rudimentary website boasts that his price will beat anybody’s. Today you are meeting with him for the first time at his office, where his hallway is cluttered with old designs and photos of homes his company has built since 1970.


You’ve come equipped with 25 questions based on this series of blogs (this is the final installment in that set of questions), because you want to avoid entrusting your nest egg to someone who knows building but is not on the cutting edge of zero energy custom home construction.


As with the three previous blogs, we encourage you to research for yourself in addition to what you learn from this column. We believe that the future is NOW when it comes to net zero energy custom home construction. It makes ZERO sense to use old and outdated conventional construction methods in Vermont with the technology we now have at our disposal. These practices will save more money than they will cost, while protecting your investment so that should you ever decide to sell and move on, you won’t end up trying to sell a home that nobody wants to buy and that banks will not loan on.


You will learn a lot by trying to answer the following questions BEFORE consulting our answers and any links that we provide with them. [Please note that in each of the four blogs related to the 25 Questions, we have renumbered the questions starting with #1, but we will review the whole list for you at the end, 1-25. See note at the end of this article.]



  1. What is the best way to ventilate a house?

    1. Attic
    2. Rafters
    3. Trusses
    4. Bathroom vents

His response: I’ve always used ridge vents, and have never had a problem, so that’s the only method I use.

Our response:

  1. There are several reasons why we believe that the roof on every home should be well ventilated; even roofs that use a form of closed cell insulation; technically referred to as a “warm roof”. This is a type of product which claims that ventilation is not necessary. We respectfully disagree.


  1. To keep the roof at or as close to the temperature outside. This will preserve the life and warranty of the shingles. Many shingle companies will not give the same warranty on a warm roof “unvented” as they will on a cold “well-ventilated” roof. The main reason is that the shingles will “bake” or “over-cook” in the hot sun and become brittle a lot quicker than they would if the roof was kept cool.


  1. To prevent ice dams in the winter. When a roof is not vented correctly, the attic space below it will warm up and melt the snow on the outside. The melted snow then runs down the warm shingles and freezes as it comes into contact with the frozen eaves at the edge. As the water freezes and builds up, it creates a dam that grows thicker and thicker with water backing up behind it until it finds a way into the house from under the shingles. This kind of winter ice dam can grow mold inside the wall cavities without showing any evidence until it’s too late to do anything about it.


  1. To prevent condensation from building up on the underside of the roof (in the attic spaces or in the rafters). Like the water that finds its way into a house from the outside, this type of inside moisture is extremely bad for the house and also for its owner once the problem is diagnosed. This problem doesn’t reveal itself until the first warm and sunny winter day in late January or early February when the roof surface warms up enough to melt the mass of ice that has built up inside the unvented and usually inaccessible roof edges and rafter cavities. It’s not unusual to get a phone call from a frantic homeowner who claims that even though there is no snow on the roof and the sun is shining bright and warm, that water is coming into the house all over the place and it’s raining inside.


Savvy builders know how to ventilate roofs and will go to great lengths to make certain that there are no dead spaces where warm air can become trapped, causing a build-up of moisture in the winter. Some houses are easier than others, for sure. For example, a simple trussed roof is the easiest roof to ventilate because there are good vents either at the gable ends or on the ridge. More about types of vents later.  With trusses, it is also easy to create vent shafts at the eaves where air movement is free and unrestricted. There are rarely any ventilation problems with houses that have a single row of trusses and good gable and eave vents. It’s still important to supervise the insulators, especially when blown in insulation is used. I can’t count how many times an installer blows insulation right into the eave vents plugging up the ventilation shafts. It takes a team effort to make certain that this doesn’t happen.


More complicated roofs are constructed with cathedral rafters. This kind of construction incorporates inverted hips and valleys where a structural valley jack often blocks any chance of air to move freely unless the builder plans ahead as to how he will do it. The bottom line is that whenever air is restricted from moving freely from the eaves to the ridge, it will eventually show up in the form of unwanted moisture.


Some houses use both trusses and rafters. There could be cathedral ceilings in part of the house and a flat ceiling in another part, allowing for the use of trusses. No matter how a roof is framed, it is usually up to the builder to make certain that it is well ventilated. 


Bathroom vents -  are a source of frustration for builders and homeowners. Even when installed correctly, they can condense inside the duct and drip backwards into the house. The proper way to install a bathroom vent is to duct it vertically until it is above the insulation and then slope it toward the outside as soon and quickly as possible. Take the shortest route and use solid pipe whenever possible. 


Other ways to ventilate your house; 

  1. Open the windows
  2. Train your dog to open the door after you leave for the day
  3. Hit the gas instead of the brake when entering the garage
  4. Put the car in forward instead of reverse when leaving the garage


  1. Is there a time when you wouldn’t ventilate a house? 

His response: Well, most of the houses I’ve built or lived in don’t need extra ventilation, if that’s what you mean. So what would be the point of adding something they don’t need?


Our response:  Our custom built high performance and net zero energy homes are so tight that proper ventilation must be provided. Some say, “A house needs to breathe.” Debates continue over how much a house should breathe. Some say they need to breathe but others assert that a house does not need to breathe. In fact, the question is rightfully asked, “Why should a house breathe?” People need to breathe because they have lungs; houses don’t, and besides, what is in a house that you want to breathe anyway, dead mice? So do we let houses breathe or not breathe? Do we ventilate or not ventilate? Wow! This is tough stuff for tired and weary builders who aren’t sure what’s going on with VOCs or air sealing, stack effects, and CAZ. Their minds are on the cost of gas, getting the mason and drywaller to show up, getting materials ordered and delivered, finding good help, worries about insurance, OSHA’s new 400-page manual, threats from the EPA of lead paint penalties, and endless commercials on TV by injury lawyers and that’s before they start the day. And what’s a CAZ anyway? [Answer: CAZ stands for Combustion Appliance Zone. It includes the area near your water heater, furnace, wall/floor heater, and/or boiler, or your gas fireplace, gas stove, gas oven, gas broiler, and even your gas dryer. If these appliances are not properly maintained or are leaking, and the spaces are not properly ventilated, a danger of unintended combustion can exist. See []


Before we continue, the following true story by, Paul, founder of Biebel Builders, Inc. and Prudent Living, Inc. illustrates how crucial it is to choose a well-informed builder for your net zero energy custom made home:


Occasionally, I've been asked to provide expert witness in court cases related to construction. One case involved a particular aging builder who had built houses since the early 1950s. In this case, a young couple had inherited just enough money to build their little dream house. But they didn’t have a bottomless bucket. It was important to them that they get every mile they could out of their money as it wasn’t a huge sum. So they hired an older builder who was known to have built small and practical houses throughout the 50s, 60s, and early 70s and would do it cheaper than anyone else - and was proud of it. I later learned that he had only built small ranches, and capes, and occasional colonials. He had never built an architecturally designed home; nothing with high cathedral ceilings and inverted valleys.


The clients had never built anything. They trusted him all the way. He was classic old school and ranked very high on the integrity meter. But there was a problem. He didn’t believe in vapor barriers or any of that new-fangled scientific stuff - and he was proud of that, also, and quick to emphasize that he had been building homes for over 30 years! What he meant was that he had done things a certain way all his life and it had always worked. He wasn’t going to have some young whipper snapper know-it-all designer telling him how to do things.


Please understand, this was a very attractive home. It had everything a dream house should have. It came complete with high cathedrals, lofts and skylights, beautiful decks, and a flowing floor plan. They got the master bathroom they had always wanted, and it was a happy day when they moved from their rental apartment into their brand new home.


Within a year, mushrooms were appearing in the sheetrock where the walls and ceilings met. Pieces of sheetrock up in the peak were turning brown and falling onto the couch below. Recessed lights had water in them in February and even the carpet in the basement had mold and mushrooms growing. I was surprised at how many mushrooms were growing. They were inside and even outside on the window trim. When I was asked by a lawyer if I would investigate all the reasons why there were such massive moisture problems with this house, I agreed. I didn’t know the homeowners or the builder.


During the hearing, when the judge asked the builder why he hadn’t performed the actions required by the design, he replied rather proudly “I’ve built houses for over 30 years and I know when a house needs a vapor barrier and ventilation and this one didn’t need it.” The judge then asked, “Then why is so much moisture collecting in the rafters, and why is the ceiling falling down? The house is nearly brand new!” The builder replied, “I was certain that it didn’t need those actions then, but it’s very true that it needs them now!” Nobody laughed. They realized that this good man had just put a nail in his own coffin by revealing his own ignorance and refusal to keep up with technology. The whole thing was a disaster. The owners lost their house and their entire investment and the builder had no money or equity of his own to give them. He was a poor old man who didn’t have a dime to his name. It was a total loss for everyone … except the lawyers. The owners ended up with no house to live in. It was eventually torn down and the land was sold with a foundation on it. Even that was saturated and blackened with mold. You may think that this was an unusual event. It isn’t! It remains a very possible scenario today.



  1. What is Geo-Thermal technology, and when would you recommend it?


His Response: Geo-Thermal heating and cooling does not make sense to me. I mean how can you expect to heat a house from well water that is likely less than 60 degrees, year round? Cooling, maybe. But it’s a lot of money to pay for a few months of air conditioning.


Our Response: Geothermal technology moves heat from the ground (well water) to the house (or vice versa). Heat pumps are used to transfer the heat back and forth. We don’t use geothermal much anymore, but we do use air to air heat pumps, because they cost less, are easier to maintain, and are nearly as efficient. [see:; and


  1. Why is Solar PV a key to net zero energy custom construction in Vermont?


His Response: Well, you have to get as much power as you use from somewhere if you’re going to produce a net zero energy home. Solar is about all there is, though in our climate I have rarely seen solar produce enough juice, due to so many cloudy days and it’s really difficult, sometimes, to mount enough panels on the house roof to satisfy the demands.


Our Response: It is a practical solution that provides balance when considering cost. It allows for house designs that people like, while still offsetting the cost of heating with a high performance home. PV systems can be mounted on the roof or on poles nearby, or both. In some cases where a net metering agreement exists between  homeowner and their local utility company, a pole mounted PV array can exist anywhere within that utility’s contract area. [See:]


  1. What are the energy saving advantages of a double-wall house?


His Response: I would not know, offhand, as I’ve never built one. As far as I’m concerned, the additional hassle and cost of obtaining and installing windows, doors, or anything else in such thick walls is not worth it. Trust me.


Our Response: Net zero energy custom homes require the highest R-factors, from top to bottom, and in this case the R-factor from double walls can be as high as R-45. Normally, a 2x4 wall has an R-factor of about 15; a 2x6 wall will average an R-factor of R-21.;



  1. How much do you charge per square foot?

His Answer: I can do it for $110 to $125 per square foot.

Our Answer: He read the articles anybody can find at:; and,


But if he doesn’t know what you hope to have installed in or around your house, from cabinets to floors, from kitchen to bath(s), from windows to doors, from decks to doorknobs. If you want to know more about accurately estimating the cost of high performance or net zero energy home construction, see our free online booklet:


This booklet is also available in printed and eBook formats from Printed:; Kindle:


Next week’s blog will feature:

A list all questions in this series, with summary answers.



Download the Ultimate Guide to Net Zero Home Construction

Tim Biebel

by Tim Biebel

Tim Biebel is Vice President of Prudent Living, a leading net zero and energy efficiency building company located in Windsor, VT.




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