Build it tight and ventilate right

Building an efficient home requires careful attention to air sealing of the building envelope. For passive homes this is even more important when attempting to achieve the air leakage rate under the passive house standards. ( for the energy geeks that's < 0.6 ACH @50 pascals)

Reach this level of air tightness requires a lot of attention to the details. In our case we have blower door that we can use in conjunction with the air sealing process to measure how tight the house is.  The blower door is used to evacuate the house and create negative pressure within the house and drawing in air from any point and with the manometer you can measure just how much air is coming in uncontrolled. Making it simple to find the leaks and seal them before the drywall goes on. To reach the passive house standard the blower door number  needed to be below 290cfm @50 and you can see from the picture we reached that number.
   Once you reach this high level of tightness, you need to provide the correct amount of fresh air into the house, we need air to live right? But how much, and do we need and do we really want it to just leak into our homes wherever it wants? Well, we know how much fresh air is needed to maintain healthy indoor air quality, a simple calculation based on how many people live in the house and how big it is. Once that is determined we want to make sure we control how that air moves into the house and how much. To do this we use a ventilation system called, Heat recovery ventilation. For most of the houses we build, this means a dedicated system of duct work to various locations in the house to move air in and out of the house. The system is much like a car radiator, in that air moves across the radiator in one direction and warms the fins. The ventilation system works much in the same way. The air is drawn out of the house in the moist locations, bathrooms, kitchen, laundry and it crosses over a radiator in one direction, warming it (in the winter). At the same time fresh air is drawn into the house and crosses over the radiator in a different direction, picking up some of the heat and transferring it into the fresh air. 65-75% of the heat can be recovered and the fresh air now coming into the home isn't just cold air but prewarmed with the air going out. We place the incoming air into the living portions of the house, living room, bedrooms, dining room.

   That's some of the technical stuff but experiencing a house like this is something you have to see to believe. Last Wednesday is was a cold blustery day the daytime high temp was about 23F with a 20 MPH wind most of the day. The wind chill in the morning was a bone numbing -6F. The house with no heat was 39F and warmed quickly with the sun shine we had that day. But what really got me was when you opened the door, no air came into the house. You could step out of the door and instantly feel the blast of cold but step just inside and you didn't even know the wind was blowing. It is really that pronounced one simple step from inside to out and the temperature dropped some 30 degrees and the wind would bite you face. Step back in with the door open and you felt nothing. Pretty cool stuff that amazes me every time we build one of these super insulated homes. Something you have to see to believe.

Stay tuned
Tom Pittsley

Let the sun shine in !

  It's getting cold out here in North Brookfield Ma and the solar windows are really starting to show their stuff. This mornings low temperature was 28F and the daytime high was only 39F. BUT the sun was shining and that's all it takes to warm this house. Late this afternoon the building inspector stopped by to inspect the solar chimney and wood stove pipe. He couldn't believe that the temperature inside this house was about 70F, on this cold blustery day. When I first met him, when applying for the building permit he was, to say the least skeptical of what were doing. This isn't your normal run of the mill house. Most of the system we are using including the SIP's envelope, HRV system, solar chimney, Heat pump, and special solar windows were things he had never seen. After seeing it work for himself I think I've converted him. His exact words were, and I quote
" This house blows my mind" John Couture, North Brookfield Building Inspector.
He couldn't believe that a house under construction could be so warm. We haven't even finished sealing up the house. We still have one door missing, that is scheduled to come in on Monday, we have a sheet of plastic covering the opening. We still need to finish foaming around our windows.
           Speaking of windows, the windows guys from Hunter Douglas are coming in tomorrow morning to commission the window shading system. If you saw the video I shot of the windows, you saw one of the shades operating. All of the solar windows along the south side of the house have an integrated shade, that retracts up into the head of the head of the window when opened. The controls for these are fairly complicated but as always Wendell, Dan and Dave, from Lamtec came through with some great work. They have designed and built a control system for the shades that gives the homeowners total control over the system. Here is a quick overview of how the shading system functions. We have 21 of the special solar windows, each of them have their own individual shade and they can be controlled in several ways. First the windows have been grouped by location, each of these zones have a thermostat that can be used to control the shades by the room temperature. The shades are primarily for use during the summer and times during the spring and fall but for the winter months the shades should be fully opened to capture as much of the solar energy as is available. The thermostats allow the house to control excess energy from entering the home, even when no one is around. This will reduce the cooling needs of the house. The have also added a push button that can be used to control a bank of windows and have the shades open or shut to their preference. The final control is a remote, that allows the homeowners to control each shade individually. Pretty cool stuff, lots of wires (1500') and a control board that looks like something out of a sci-fi movie. Hopefully by the end of the day tomorrow all of the shades will be operating. That's a good thing because when we installed the shades we left them partially down and right now we aren't even capturing all of the energy we could be. With the shades in their current position were a losing about 20% of the energy and on these cold late fall days we can use all of the suns energy we can.

If the building Inspector is blown away now, wait till were done tightening up the house and it really starts work!

Stay tuned Tom

Metal roofing, a very green product

Metal roofing is a very green option for several reasons. First of all it can be designed with almost no waste. Most roofing materials have at least a 10% waste factor. The elimination of waste means less materials purchased and less waste to dispose of. What little waste there is, is 100% recyclable. Metal roofs last longer meaning less maintenance over it's lifetime, it is likely the Melad's will never have to replace this roof in their lifetime.     

The one thing that creates more work and by more I mean a lot more, is the chimney sticking up out of the roof. This one feature of the  house turns 4 pieces of metal roofing into 35 different pieces that all need to be custom fabricated to correctly flash round it. It takes more time complete than the rest of the roof along the south side. The rough plumbing and electrical has been completed. On to the siding, HRV, solar chimney and heating system next.

Tom Pittsley

Solar chimney? What is it? and some really important steps to insulating a foundation

We are using a passive solar cooling technique in this home that is referred to as a solar chimney. A solar chimney is a little hard to explain but I will do my best. To fully understand how a solar chimney works you need to know a little bit about building science and the term commonly referred to as the " stack effect". The stack effect is what happens within a home when warm air is allowed to escape from your roof or through your attic. Something we try hard to stop in most homes by air sealing the attic space. The pressure created from the stack effect causes air to be drawn in from other places in your home, commonly your basement or a leaky envelope and windows within the home. Not something you want to do on a normal basis. The higher the point in which the air escapes the higher the pressure gets.

   This home uses the stack effect to our advantage. We are building a box located on the roof of the home. This box will not only contain the wood stove pipe but a whole house fan system as well. This box ( chimney) will be uninsulated and covered with a dark siding material. The heat created within the chimney will want to rise and escape from the vent pipes located on top. When the insulated (R-38) doors to the whole house fan system are opened, this will create negative pressure within house. In this home we are able to control where the air entering the home is able to come from. We have placed windows low to the ground on the north side of the house that need to be opened to allow the chimney to work. This will draw cooler air in from the north, fully shaded side of the house. If the system does not provide enough natural ventilation the whole house fan can be turned on to really move the air through the house. While not enough research has been done on solar chimneys to fully calculate how much cooling effect this will have on the house. It will be interesting to see how well it works next summer. What I did feel was the effect it will have on the building when constructing it. The last piece of the chimney was the top and when I was placing it I had to hold it down and could feel the air trying to escape, it wasn't even a warm day.

Foundation insulation, important steps!



  Foundations in most homes have little or no insulation at all and it has a negative effect on the whole house. Most basements here in the northeast contain the mechanical systems of our homes.( heating, domestic hot water and cooling) When these spaces are not conditioned we loose a percentage of our energy to this location. Conditioning this space for most homes means running a de-humidifier to control the moisture and consuming a large amount of electricity in the process. In this home we are using a better approach that includes insulating the foundation on the exterior from the footing all the way up to the sill of the home. We are using a product called Geofoam that is made of high density EPS, 2" thick with an R-11 insulation value. While building codes here in MA require you to insulate your foundation most builders stop this insulation at ground level, leaving a large hole in the homes thermal envelope. It does create additional work ( insulation, stucco and flashing) to do this but the result is a much better home in the end.

The other area of the foundation that needs attention in the basement floor or slab.

In this home we also insulated under the entire floor of the slab and up the side of it as well. This is commonly referred to as a thermal break, we have stopped or slowed the movement of thermal energy from moving through the basement floor. Along with this we place a 6-Mil vapor barrier under the concrete to stop the movement of water through the slab also. This eliminates the need for an energy hogging de-humdifier.

      When attempting to reach the standards for passive solar homes, all energy uses need to be considered. From the top to the bottom, no details is to small to overlook and in the case of the foundation,

it is no small detail.

 To finish off the foundation insulation, we simple cover it with a stucco and flash to top of it. Once again a little more work but in my opinion well worth the efforts.

Stay tuned

Tom Pittsley

tom.pittsley@nextsteplivinginc.com

Solar windows are really heating up

I did a little video of the windows in action over the coarse of a day. It was pretty impressive to see just how well they work. They video gives a better explanation of how the windows work as a system to not only capture and store the suns energy, but also how to control it as well.




I can't wait to see how well they work once the doors are installed.

Some other things that have been going on on the site is the interior framing, that was completed earlier this week. Along with installing the vapor barrier and insulation under the basement floor. Yes we not only insulate the exterior of the foundation but we also insulated under the basement floor and up along the sides of the concrete, eliminating a thermal break in the envelope of the building. Combining a highly insulated thermal envelope with air tight construction is what make a passive solar how possible. The higher the insulation level the lower the energy costs needed to control your indoor environment.

  This coming week we will be installing the solar chimney. What is a solar chimney? Stay tuned and find out.

Tom Pittsley
tom.pittsley@nextsteplivinginc.com

Our Solar windows are in !

The new solar windows for the house went in last week, just in time for the Green building tour this weekend. It was a tough week to say the least with 4 out of the 5 previous days filled with rain, around 4 inches. On Tuesday morning we finished installing the last of the SIP's roof panels, by Wednesday noon the roof was papered in and weather tight. At the end of the day on Friday, 19 of 21 the solar windows have been installed.

On Saturday they finally got some sun and started to show their stuff, as the windows reached around 110F by 4 in the afternoon. We left one window with the shade down fully to see how much of a difference the exterior solar shades make. The results were pretty impressive as the window with the shade down only reached 70F. Saturday was not exactly a warm day with a morning low of around 40F and a daytime high of only 63F, a slight breeze blew through the house as the other windows have not yet been installed. I can't wait to see how well they work once the house is buttoned up. Here are some IR images of the window at 4PM one with the shades up the other with the shade down all day.  These solar windows are unlike anything you have ever seen. The windows contain 4 layers of glazing, two cavities filled with argon gas, a couple of lowE surfaces and a 1-1/4" layer of clear gel. The gel acts as a thermal mass, storing the thermal energy within the window itself. The combination of glazing gives the window a U-value of .2 nearly 50% better than an energy star rated window for insulation value. Here is were it really differs, these windows have a Solar heat gain coefficient of .72. This means that 72 % of the solar energy is transferred through the outer layers of glass. This energy is then captured right at the point of entry into your home, within the gel. These windows are very heavy, about 250lbs. per unit, (26-1/2"x77-1/2") Each window contains about 170lbs of mass, this means for each degree above room temperature these windows go you have stored 170 Btu's of thermal energy. Raise the temperature to 110F like we did last Saturday and the thermal energy stored is 6,800 Btu's per unit. We have 13 windows that contain thermal mass within the window, this means we stored 88,400 Btu's of thermal energy in the windows of the home, over the course of one day. That is about equal to one gallon of oil burnt in an 80% efficient boiler or about one thermal of gas.       So, that's great right? but what about cooling? Notice the shades in the photo above. These shades are integrated right into the window frame and retract up into itself. The final arrangement of the controls is still being worked out but here is how they are designed to work at this time. The windows all have home run wiring back to the control panel, custom built for this project. The windows are then broken into groups according to location within the house. These groups are then controlled by a thermostat placed within the each zone. If the zone gets to warm the thermostat will send a signal and shut the shades. The really cool part is the remote control that gives the homeowner total control of each individual shade. When these shades are left closed the SHGC drops to .14 making this a energy saving window on the cooling side as well. I will post some more pictures and videos of the windows in action over the next few weeks. Stay tuned Tom Pittsley tom.pittsley@nextsteplivinginc.com

Lots of good stuff happened this week

Tuesday morning National Grid showed up to turn our power on, what a great day. After the last few weeks listening to the generator running it was nice to have have peace and quite. Well not exactly quite, with the compressor, saws and nail guns all day long but still much better than listening to the generator.

Some of the other things that happened this week.

I picked up the first 4 of our solar windows, man are they heavy. These windows have 4 layers of glass, with a 1" thick layer of clear gel encapsulated between 2 of them. Each of these 2'x6' windows weighs about 250 pounds, it's a good thing I have a one ton truck. These windows capture and store the suns energy within the gel layer and then radiates it into the house at night. They also have an exterior solar shade that retracts up into the head of the window that shuts the suns energy off when it's not needed. If you have the chance come by and see them for your self at the tour next weekend.
   
 We finished the last couple of wall panels on Monday and the rest of the week prepping for and installing the roof panels. Installed our triple 16" x 48' LVL ridge beam and got more than half the roof panels installed. only one week left until the Green building open house tour, next weekend and still a lot of work to do.

Tom Pittsley
tom.pittsley@nextsteplivinginc.com