Residential Issue: Monterey Bay, California
Radiant Architecture Winter 2010
This month's project sits on what many California homeowners might consider the holy grail of construction site. Perched on the cliffs overlooking one of the great surf spots on Monterey Bay, this site has south facing views that are unobstructed but for a single lane road running between the home and the ocean. Yet this incredible view property inherently posed numerous challenges that demanded great creativity from Matson Britton, the project architects. It was a given that the south facing fenestration be maximized to take full advantage of the striking views. Mitigating the impact of the road in front of the home dictated a two story reverse floor plan to put the primary entertaining areas and views well above the road. But the large window walls that result from this approach reduce the lateral load resistance essential for good seismic design and this site is only a few miles from the epicenter of the 1989 Northern California earthquake. This challenge was further exacerbated by the owner's strong desire for the comfort and energy efficiency of radiant floor heating. Years ago, radiant was traditionally integrated into high mass slab floor construction. But high mass is the enemy of good seismic design. Matson Britton solved the seismic design issues in part by using a low mass radiant panel to reduce the lateral loading and using extensive steel moment frames to provide adequate lateral resistance for the remaining load. The particular radiant panel used here frames like a standard 1-1/8" thick sheet of conventional 4x8 subfloor so the odd discontinuities between steel and wood framing were not a problem. This panel easily integrated into the complex hybrid steel/wood framing plan, while providing the high conductivity/low mass that good structural and mechanical engineering required. The low mass of this system provided another important benefit. Northern California in the winter can be 25° at sunrise but by mid afternoon, on sunny winter days, the temperature can rise to near 60°. With large south facing windows capable of considerable solar gain when the usual marine layer clears, an old fashioned high mass system would have been incapable of adjusting its output rapidly and precisely to the changing heat load. A common complaint about radiant in the past was that a home might be too cold in the morning followed by being too hot in the afternoon. But the low mass system used here quickly and accurately adjusts its output to provide the constant comfort that the owners, Gerry and Alane, required of their radiant system. Architect: Martha Matson, Matson Britton Architects Matson Britt on was founded in 1988 and specializes in custom residential and commercial projects. Their work can be seen throughout the Bay Area in Northern California. Matson is a self-described huge fan of radiant. Rapid recovery was really important on this particular project because we were designing for an indoor-outdoor lifestyle. I really just can't say enough about radiant and Warmboard in particular because its quick response matches the system output to the changing needs of the structure, which is extremely important for energy efficiency. And because Warmboard is a very flexible product that can be used with various floor coverings, it gave us tremendous design freedom. In the past, traditional slab systems severely limited the use of hardwood, but as you can see from the photos, the beautiful nailed and finished in place hardwood floors are one of the strongest elements in the interior design and essential to the Asian Modern theme of the home. The house was designed with steel moment frames and using a radiant heating technology like Warmboard facilitated that. It's not possible to run ductwork through a structure like this without soffits and chases which would intrude on the clean opens spaces which were essential to both our design theme and the vision of the homeowners, Gerry and Alane. Our goal was to create a unique home that would allow the homeowners to take full advantage of the temperate climate of coastal California, whether enjoying an indoor-outdoor lifestyle by themselves, or when entertaining. Using Warmboard was ideal for reducing heat loss. Because radiant floors tend to heat the home itself, not just the air, the rate of heat loss from open doors and windows is far lower than that of forced air systems. Warmboard was also the most logical choice for this project due to the use of stone, tile and hardwood as floor coverings. Using Warmboard also allowed for quite a bit of flexibility regarding what part of the home would be actively heated at any given time. This was accomplished by using numerous zones. The Warmboard design team was able to accommodate a zoning plan that met all of our design requirements. Their detailed construction documents were easy for the contractor to bid and easy to follow during construction. The low mass in combination with the high conductivity of the thick aluminum clad panels ensured that unused rooms kept unheated for energy savings could be quickly brought to a comfortable temperature when needed." - Martha Matson Matson Britton Architects ph. 877.877.3797 www.matsonbritton.com Contractor: Bret Gripenstraw "I've been a contractor for over twenty years and have been using radiant in a lot of my jobs for about ten years now. It's a very good choice for homes like this with all the steel framing. You can't run ducting easily through a home like this so radiant helped me avoid all the hassles that ductwork would have required. I've done over twenty radiant homes. My first radiant experience was what's called sandwich method, which involves a lot of pieces of aluminum, lots of little strips of wood, a second subfloor and a lot of labor. I'll never do that again. I've also done three thin slab jobs but pretty much all I've used lately is Warmboard. I like it because it gives you all the options for all the different flooring. When you do slab systems it's hard to put hardwood or carpet down. The flooring throughout most of this home is Brazilian Rosewood, nailed, sanded and finished in place. The owners wanted a high gloss finish. Warmboard was the only practical radiant option for these kinds of floors. Gerry and Alane always wanted to use radiant because they saw a number of the homes I built and they just liked everything about radiant, the energy savings, the comfort, the air quality, the quiet. They're really happy with their system. I recommend radiant on most of my projects precisely because it keeps my clients happy and happy clients give me good referrals. Part of my preference for Warmboard in particular is that my crew is real familiar with it so we have no surprises or cost overruns. This home's complete heating system came in at about $14/sf which is right about what other methods have cost me but with this system I have so much more versatility." - Bret Gripenstraw Bret Gripenstraw ph. 831.818.9519 Homeowners: Gerry and Alane " We decided fairly early on in the whole process to use radiant - it's more efficient, more comfortable, and we were happy to avoid the allergens and other particulates you get with a traditional heating system. Fortunately both our builder and architect were long time advocates of radiant as well. I think that between them they've used virtually every option available at one time or another so we were comfortable relying on their experience. They recommended that we go with Warmboard and we're really happy that we did. We are especially happy our choice allowed us to have flooring this beautiful. These floors were an important part of the Asian Modern vision we had for our home. And our energy bills are incredibly low. Our house is always a comfortable temperature whether we open it up to the outside decks and balconies or even when the weather rapidly changes as it can near the coast. We love our new house, and are really happy with the work that Martha Matson and Brett Gripenstraw did. Brett and Martha took what we couldn't quite see in our minds, but knew that we wanted, and translated it into a beautiful, efficient, and extremely well-made home." - Gerry and Alane
Understanding Radiant Technology
From Terry Alsberg Warmboard's inventor The technologies in this home, from the active and passive solar features, advanced steel framing, and of course a state of the art hydronic heating system would all make good topics for my technology column this month. But when I looked at this home what struck me most were the beautiful Brazilian Rosewood floors. There's hardwood and there's hardwood, but these are at another level. You almost don't want to walk on them they look so perfect. And yet the old thinking with radiant floors was that proper nailed down hardwood, sanded and finished in place was a no-no. So let me take the time here to revisit a number of outdated assumptions. The heat from a radiant floor will not damage hardwood. The Radiant Panel Association guidelines for radiant installations stipulate that floors should not exceed 85° and for most modern, well insulated, homes floor temperatures are rarely above 80°. If we think logically about this, air conditioning has become prevalent only in the last 50 years, which means that hardwood floors have been getting well above 85° in the summer, for the thousands of years that hardwood floors have been used. This means that normal radiant floor temperatures are no hazard to a hardwood floor. The right cut of hardwood over radiant will not significantly cup, warp or gap. This has more to do with the cut of wood and its moisture content when installed, than the heating method. All hardwood floors are a natural material, and by their nature, will show movement through the cycle of the seasons regardless of the heating method. The National Wood Flooring Association website (woodfloors.org) speaks about this and says that seasonal gapping can be expected in any home. If the moisture content of the planks is properly controlled through acclimation prior to installation, any gapping will be quite minimal if at all. Cupping is exacerbated by the cut of the planks. If the annual rings are vertical (quartersawn) or close to vertical (rift cut), cupping is virtually eliminated. These subjects are covered extensively at warmboard.com/hardwood. You don't have to use a floating floor with radiant. Of course floating floors will work fine with any radiant system, but some homeowners, like Gerry and Alane, prefer the solid feel of a nailed down floor. And there is no substitute for the beauty of a sanded and finished in place hardwood floor. Because Warmboard is 1-1/8" thick, it is ideal for nailing hardwood to. Because the tubes are clearly visible to any hardwood installer, it's easy to nail into without hitting any tubing. And because the plywood has similar moisture content to the hardwood itself, it does not alter the moisture content of the planks as moisture laden slab systems frequently do, which helps minimize the natural movement of a wood floor. Even floor temperatures are essential. There's always some variation in temperature across the tubing pattern in any radiant floor. But thick aluminum keeps this to a minimum. This is because the more conductive a panel is the more even the floor temperatures will be and this is an important contributor to the comfort of a Warmboard radiant floor. But another important benefit of high conductivity is that the more even the floor temperature, the more stable the hardwood will be. The beauty of these floors in this home vouch for the success of this installation. Bret Gripenstraw's extensive experience with radiant tells him that hardwood and Warmboard make an excellent match. The desire for traditional hardwood flooring is among the most frequently cited reasons for choosing Warmboard.