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Q: I'm installing 1,100 square feet of hardwood flooring over a radiant heat system. How can I be sure that there won't be any problems down the road?
A: Radiant heat systems are gaining a lot of popularity with homeowners and businesses alike. In fact, questions about radiant heat systems are one of the most frequent calls we receive on NWFA's technical hotline.
As a wood flooring contractor, you probably have heard horror stories about radiant heat installations that have failed, but many more successful installations have occurred than not. As with most other types of installations, taking the time upfront to learn all you can about the type of system you will be working with, as well as educating your customer, can save you a lot of trouble down the road.
With so many different types of systems available, and so many different technologies involved in each type of system, it is difficult, if not nearly impossible, to keep up with all of them. The problem is that each type of system can affect how you approach your installation. This is why you need to have a full understanding of the type of radiant heat system you'll be working with on every job.
During the past 10 to 15 years, there have been many improvements in radiant heat systems. Many of these improvements have benefited flooring contractors and made our jobs a lot easier. The most significant improvement is that the systems now are more efficient, so the temperatures they produce are not quite as high. This is a key factor in the long-term life of the floor, since excessive heat literally will cook the floor and cause problems.
One of the most common problems that occurs when installing wood flooring over a radiant heat system is when the contractor requests that the system be on and running before and during installation. Unfortunately, the system often is turned on without proper temperature control, which can cause it to run at full steam, essentially baking the flooring material. Of course, we all know that the proper approach, as with any type of flooring installation, is to allow time for proper acclimation of the flooring.
To acclimate flooring properly in a radiant heat installation, make sure the system is turned on at least seven days prior to delivering the wood to the job site, and that the environment is as close as possible to actual living conditions. You may need to allow even more time depending on the type of substrate. Gypcrete or concrete substrates are good examples of materials that need more time for proper acclimation. This is an important step to take, even if the installation will occur during the summer. If this step is skipped, and the system is turned on for the first time during the winter, moisture will be cooked out of the substrate and will go right into the wood flooring. This can occur even if moisture levels were checked and determined to be acceptable when the installation actually occurred. This is because the heat, which is being introduced for the first time, is forcing the moisture out of the substrate and into the wood. If this moisture moves into the wood too quickly, which is likely with the excessive heat, cupping probably will occur.
As a flooring contractor, you need to make sure the products you sell for radiant heat installations are as stable as possible. Also keep in mind that the more narrow a product is, the less movement the product will show. Different species of wood also have varying degrees of stability. For example, mesquite and quartersawn materials are twice as stable as some other materials. In addition, darker woods will show gaps much less than lighter woods, such as maple, ash or white pine.
Another helpful tip is to have three thermostats available on the job site: one for water temperature, one for room temperature and one for outdoor temperature. This can help eliminate a common problem: People wait until the temperature drops significantly outside and then turn on their radiant heat systems full blast, again causing excessive heating and moisture problems. This can happen even in a home with an existing system, and can occur on a yearly basis. The best approach is to turn on and introduce the radiant heat system slowly, so that the wood acclimates properly and is not adversely affected by the quick introduction of excessive heat. Of course, tighter moisture content measurements between the flooring and the substrate go a long way toward preventing problems down the road, as well.