Why new homes are exposed to more moisture
High energy costs have contributed to new homes being built very energy efficient but this creates a problem as they are too tight. Vapour barriers meant to stop air movement are trapping and holding the excess moisture in the new home. Indoor air quality is worse than outdoor air quality: gases, moisture and odors are trapped inside. Houses are more energy-efficient, but comfort, health and any wood products inside the home are put in unfavourable conditions.
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Breaking down the stages of building a new 2000 square foot home with a full basement showing the amount of water introduced at each stage is quite shocking and almost unbelievable.
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The poured foundation and floor can have up to 1200 gallons of moisture. This moisture will slowly ooze out of the concrete in the form of vapour over the next 1.5 to 2 years at a rate of 2-3 gallons per day. I can’t imagine this vapour being the healthiest to breathe so removing it quickly is a good idea and not allowing it to linger is a good idea.
The framing and other wood products will add another 800 gallons of moisture to the new home. This moisture also leaves the structure gradually over the next 1.5 to 2 years due to the vapour barriers. If allowed to linger the stagnant moisture in the walls can turn to mold which is a huge problem so remove this moisture quickly. Just because you can’t see it doesn’t mean it’s not there. Once the home is closed in, get the commercial dehumidifier running in the basement.
Drywalling, taping and mudding can add 100 more gallons of moisture to the structure. This is mostly surface moisture that will be released much quicker over a few weeks. At this stage the dehumidifier should be running in the basement removing this moisture. You do not want the flooring in the home at this stage. Do not drywall the ceiling in the basement as this traps the moisture not allowing it to leave the structure causing long term cupping.
Priming and painting adds up to 80 gallons of moisture to the structure. This is all surface moisture that needs to be removed immediately. Continue running dehumidifier. Wood flooring should not be in the home.
Tiling and Masonry fireplaces can add 50 gallons of moisture. This moisture will take a few months to be absorbed by the air.
The new home is saturated with up to 2230 gallons of moisture that will be released slowly over the next 1.5 to 2 years. This 2230 gallons of moisture is why a commercial dehumidifier capable of removing at least 10 gallons per day is needed. A commercial dehumidifier in the basement running for 60 days at full capacity should remove 400-600 gallons of moisture which is a great start. The goal of the builder should be getting this loose or surface moisture removed by closing time and pass on information to the new home owner stressing how important continuing this dehumidification process is until all new home moisture is removed.
If this 400- 600 gallons is removed with a commercial dehumidifier prior to closing the homeowner can purchase a smaller dehumidifier capable of removing 3-5 gallons per day which should keep up with the moisture being released by the structure and concrete. Set the dehumidifier at 40% Relative Humidity and it will run only when needed which saves electricity. The high humidity summer months will require more moisture to be removed. When a problem occurs with a hardwood floor it is unfortunate the builder says “We never used to have these problems” and blame it on bad wood. Wood has been kiln dried to a moisture content between 6-8% for more than 75 years and the milling process is the same so it is difficult to blame the issues on the wood especially when it is perfect when initially installed. The problem is very simple. Homes are being built much quicker and much tighter than in the past. The moisture is trapped inside and is gradually absorbed by the wood flooring very slowly until the problem is visibly noticeable. The biggest challenge is get your subfloor within 2% of the hardwood flooring and continue the new home moisture removal. Our Allglobe or Aquabar underlay separates the hardwood and subfloor temporarily but eventually the moisture gets through and the problems start if the subfloor moisture hasn’t been removed. It is almost guaranteed especially in the humid season if there has been no attempt made to remove this moisture there will be a problem.
Depending on the season it is very likely the subfloor has been rained or snowed on. The wall studs and joists are saturated with the same moisture. The newly poured concrete floor and walls are curing and increasing the humidity in the basement which is getting absorbed by the bottom of the subfloor. Not to mention the water lying on the basement floor from the rain that will be there until the house is closed in and HVAC system is running. The hardwood flooring is the driest product in the house and will slowly absorb the excess moisture from the new home causing it to cup and crack. Is it realistic to think this moisture oozing out of the home will not affect the hardwood flooring which is the driest product at the site? The hardwood flooring should be the last job completed on the site for 2 main reasons. The first being limiting foot traffic and trades people working over it to prevent surface damage. The second being the extra time gives the subfloor more time to dry as well the subfloor dries much faster when both sides are exposed.
It seems pretty simple. Why would people not follow your advice?
This is hard to understand. If you went to your doctor and got a prescription for an illness and never took the medication would it be your doctor’s fault? We have builders that follow our advice and have very few issues. When they have an issue we are always there to help find a solution. Unfortunately some builders take every possible shortcut and when things fail they are quick to make someone else accountable.
If you know the new homes are wet why dry the wood so much and avoid the big problem of the new home moisture?
That is a great point and would solve the problem for the first 1.5 to 2 years but once all the new home moisture left and normal living conditions were created you would be left with large permanent spaces between boards which would be unacceptable. It is unfortunate that builders would rather blame the product then follow our simple guidelines.