Passive solar home construction: Walking the walk

I have been talking the talk for a long time, but walking it is a different story.


Building a passive solar home and designing one are two different things, measuring it's performance is another. While over the years I have built several homes that were designed for passive solar all to some varying degree. In 2008 I had the chance to design and build a passive solar home for Linda Johnson and her two children, Rachel and Max. After over twenty years of construction, the last ten having been dedicated to building better buildings, I finally had my chance to use my years of knowledge as a Design/Builder to create the most energy efficient home I have ever built. It was great to work with a home owner to design the home of her dreams, while I focused on ways to reduce the energy demands and cost of the homes construction. Below is a list of the house specifications, along with the total energy usage to date.





Location: Middleboro MA

Size: 1,976 sq/ft = 183.5/sqm


style: Modified single level ranch style

3 bedroom, 2 bath, kitchen/dining/living, laundry, utility, and entertainment/wetbar


Oriented to capture as much passive solar as possible 180 degrees south along long side 68'

Roof slope maximized for active solar to be added in the future, conduit in place

Cost of construction $269,000 plus extras and appliances total cost of $290,000

$135 sq/ft base costs $145 sq/ft final cost

10% ratio of floor to south facing glazing,196 sq/ft, 46 sq/ft conventional,
150 sq/ft of specialized thermal mass windows: More info on these windows

Completely insulated slab-on-grade foundation w/integrated radiant heating/cooling R-15

6-1/2" Structural Insulated Panels for all exterior walls R-24

10-1/4" Structural insulated panels for the ceiling 1,300 sq/ft R-40, conventional frame above

7" of closed cell spray foam in cathedral roof section between conventional rafters,940sq/ft R-40

Additional insulation at sill points to address thermal bridging

Air sealing,using negative pressure during construction to find and seal all air leaks

Heat Recovery Ventilation system w/programmable control

Ground source heat pump to provide heating and cooling to the radiant slab

Energy efficient appliances

Whole house De-humidification system

All energy supplied to the house as Electricity

Date loggers to record efficiency of systems and monitor comfort levels for Temp/Humidity

The standard for total annual energy use under the Passive house Institute standards is < 120 KWh/Sqm. To meet the standard this house would have to use less than 22,000 Kwh's annually: 183.5X120=22,020.
While the house is about to undergo it's first New England winter while occupied, the performance to date has been consistent with the energy model. The house has been occupied for 6-1/2 months now and the total energy used to date is 6,020 Kwh's. If it continues through the winter meeting the expectations the total annual energy consumption will be around 12-14,000 Kwhrs surpassing the standards set by the passive institute by 33% or more. While I didn't do a blower door test to measure the air leakage rate or have a way to separate heating energy from total energy, the final Kwh's of energy consumed will be the measure. No complicated measure devises and costs, just the electric meter the electric company provides. We have been logging the energy use by simply reading the meter at different intervals and recording the actual energy consumed. On April 20th 2010 the house will have gone through one full year of occupation, on that date I will be able to confirm if it has met or exceeded the standard.

It's going to be a long winter's wait !

Tom Pittsley
ecobuilder@aol.com
www.eebt.org

Window shading for a passive solar home

We just finished posting a video on YouTube showing how well the window shades developed to compliment our thermal mass window system work. while it was specifically designed to work with the thermal mass windows, these shades can reduce the cooling needs of any home that experiences solar heat gains during the cooling season. These are the first prototypes to be installed on a home and are functioning to reduce the cooling needs of this home dramatically. I will post more about the geothermal cooling system when I have some time, but lets just say that is far from conventional.




Tom Pittsley
ecobuilder@aol.com
www.eebt.org

Solar green home completed and performing as hoped

So, it's been a while since my last blog. In the beginning of April, we held our open house. It was great, we had over 75 people come by and take a tour. The homeowner has since moved in and is enjoying her new home. In mid February we first fired up the heating system in the house and have been monitoring it since that time. During the first 32 days of the heating system running and the cold house being brought up to temperature, we consumed $157 worth of energy. Keep in mind this house is entirely heated by passive solar energy in combination with a geothermal heating system. The geothermal system is supplying the radiant floor slab with heat at 90-95F and maintaining the house at a very comfortable temperature even on the coldest days of February. I have to say the geothermal system is not a plug and play system. I installed data logging devices to monitor the system and the on/off cycles of the heat pump. After the first few weeks and some tweaking of the flow rates and delta T of the storage tank we finally found the right mix to make the system run at it's peak performance. What I have found is that very small changes to the flow rates can have a profound impact on how well the system runs. After all what good is it to have the most efficient heating system if it isn't working at it's peak.
We still have the solar hot water system to add to the house, we will be installing this in the next month or so. As of right now the domestic hot water is running on an electric hot water tank. Most people would think that this is not the most efficient way to heat water and I would have to agree with them, it isn't. So why would we put an inefficient hot water tank in a home designed for zero energy? I won't try and get to technical, but here are the basics needed for a solar hot water system. First you need a collector, then a storage tank, some piping, a pump or too, a controller including temperature sensors and an exchange, usually found inside the storage tank. What I have chosen to do in this case in separate the tank and the exchanger rather than combining them and here is my reasoning. Simple solar storage tanks are no different than a traditional electric hot water heater, other than a couple of existing ports to make the connections. These can be simply added to any existing electric hot water tank by adding a T at the intake and the drain port on the bottom. The cost difference is the thing, a tank sold as a solar storage tank usually costs twice as much and typically even more. What about the exchanger? Some tanks have an exchanger already inside of the them and they work excellent, but at what cost? Most of the solar tanks, that have the internal exchangers cost at least $1500 typically more like $2,000. If you separate the components and make the exchanger and the tanks separate you not only reduce cost dramatically but you also reduce maintenance costs down the road. By using and external heat exchanger you do loose some efficiency but not much. What do achieve is a system that individual components can be changed out as they fail, (somewhere down the road) without having to throw away the tank because the exchanger failed or visa-versa. Reducing the initial costs and making the system modular makes sense to me, what do you think?

The total energy cost for the house from Mid February till now has been about $400, not to bad given the cold temperature we experienced during Feb and March. So, this all electric house is ready for the next step, solar electric or PV as it's better known. For that we will have to wait, at least a year before making the decision as to the value of such a system. The cost for doing this has come way down over the last year and once the years total energy usage is determined then a system to meet these needs can be designed. all of the infrastructure for this is already in place. If my calculations are correct this home will need a 6K Pv system to meet the homes needs at a cost of about $35,000. It's hard to justify such a system if the total yearly energy costs are $1,500 as predicted by the energy modeling done before the house was even built.

I little tidbit about just how energy efficient the homes envelope system is, when compared to other homes and even some extraordinary ones. A typical home built in this area and insulated to meet the existing energy codes would use more than 2.4 times as much energy for the heating and cooling needs. Even a house designed for the Solar decathlon competition doesn't come close the efficiency achieved with this design. I am currently acting as an advisor to the BAC/Tufts University solar decathlon team, were they are currently building an 800 sq/ft home completely powered by solar energy as part of the DOE's Solar Decathlon competition. Their home, while being a great model of solar energy has a heat loss equal to my 2,000 sq/ft home. This house has a 11 Btu heat loss at design temperature. That means that the heating system for the house was so small we used the smallest one we could find to meet the heating and cooling loads of the house and it was still over sized by 30%. The maximum design loss for this house is 20,000 Btu's/hr at design temperature. That means this house will only use 20,000Btu's/hr when the outside temperature is 0 degrees and the sun isn't shining. Most homes heating systems are rated for at least 60,000 and most are more like 100,000 Btu's.

That's all for now, but stay tuned I will be shooting some new video's of the home including the new super low maintenance lawn we installed a few weeks ago. Pretty cool stuff, never needs watering once established, grow so slow you only need to mow it 5 or 6 times a year and never needs fertilizer. I hope it lives up to the expectations put out in the literature about this product, if it does I will be replacing my lawn next year. I love the idea of not having to spend a couple of hours every weekend mowing my lawn. Stay tuned.

Tom Pittsley
ecobuilder@aol.com
www.eebt.org

Passive solar home performance update

Here is a video with a quick update of how the house is performing, now that we have the geothermal heat pump up and running. Better to watch, than to try reading my writing!!

Stay tuned, the videos of the acid stained concrete floors is being work on and should be up in the next few days. These floors, while incredibly labor intensive, have a look, a feel and warmth you have to see to appreciate, people can't belive it's concrete. One of my friends, who is also my greatest critic, responded with a WOW when first seeing the floors. That's the kind of response you will have once you have seen this, come by for the open house and see it for yourself.

Open house coming in April, date to be announced.




If you are interested in building an energy efficient, passive solar or active solar home, that is what I do. Want to go all the way to zero energy? We can do that too. For more information contact me at ecobuilder@aol.com

Geothermal heat pump system

Although the house is using the sun to heat itself, there is a need for additional heating during the cold winter months when the sun isn't shining. For that purpose we installed a geothermal heat pump system to deliver the needed heat with the utmost efficiency. Yes, the system was costly but given how efficient it is, and the desire to have the home completely run by electricity, it was the most sensible option. The house is designed to be convertible to zero energy, once the total energy loads have been determined. ( PV array) The heat pump reduces the amount of electrical energy needed to heat the home.
How does a heat pump work? That is a sum what complicated answer, but the gist of it, is that it moves heat out of the ground and transfers it into you house by using a refrigerant, compressor and an expansion valve the system extracts heat out of the ground exchange while in the low pressure cold side of the system. Not the simplest thing to understand, how you can move heat efficiently even at temps as low as 32F, but it really works and works well. The other component of the system is the radiant floor slab, which allows for low temp water for heating. Once you have reduced you need for heat through super insulating and air sealing the systems cost is dramatically reduced. For this house we purchased the smallest heat pump that we could find, that would not only provide heat but also provide cooling.
Here is where we stuck our necks out. Not many people try and cool their homes through a radiant floor and there are several obstacles to doing this. First of all most houses require more cooling because the are not super insulated, radiant cooling has a limited amount of Btu's it can deliver. Another major obstacle is humidity and condensation which can accumulate on the floor, if you have rug, wood or vinyl this could be catastrophic. We have installed a whole house dehumidification system that can reduce the humidity in the air and also reduce the demand for cooling. You feel cooler when the humidity level is lower ( it's not the heat it's the humidity) reducing the need for cooling. But when there is a demand the humidity level can reduce the dew point and reduce the chance for condensation. Another part is the ceiling fans which may reduce the need for cooling or at least help to move the cool air off of the floor and circulate it around the room. If we do get condensation on the floor, it is not a major problem. The finished floors are stained concrete, so they won't be ruined if it happens and they won't hide the problem under the rug, making it easy to identify and rectify. Here is a video showing the heating and cooling system.



The closed loop, horizontal ground exchange system was shown on a previous video and gives you an idea how the ground exchange is installed.

This is one feature of the house that has been gaining in popularity in the last few years. It makes your energy cost less susceptible to the fluctuations of the fossil fuel market. Electricity cost do not rise 100% in a few months like the oil prices did over the last year, and enables this house the ability to produce all of the energy it needs to maintain itself. To make the final leap to zero energy is a costly one and given the inefficiency and cost of PV panels at this time it is not the most cost effective approach. However I do believe that PV will get better and the cost will come down, to that end an electrical chase was run from the attic space into the utility room for future use. The roof line was designed to maximize the solar gains and make use of all potential solar energy that is available on this site. Hopefully one day soon, the PV manufacturers will make a panel that is at least 30% efficient and costs less than the house itself. At this time the cost to install PV panels that would produce all of the homes energy needs would be between $40-50,000 and would take the full life expectancy of the panels to pay for itself. Not there yet!!!

Tom Pittsley
ecobuilder@aol.com
www.eebt.org

Green Building, from the ground up

While most of my blogs have been focused on passive solar energy,there is a whole lot more to building an energy efficient or "Green Building". I don't like to call myself a green builder, it sounds kind of trendy and that has never been my thing, but I have been following most of the basic principles for years. Lots of the things that are thought to be green also save money during construction, things like reducing material waste. My current project, has had half of the normal waste of a typically built home, great for the environment but also great for my wallet, I saved almost $1,000 in disposal fees for the project. I have at the homeowners request decide to attempt, to compile all of the green elements designed into this house. My latest video covers some of the features.


I want to take a minute to mention and thank Linda Johnson, (homeowner) without her this project would not have been possible. When Linda first came to me in June of 2008 and told me she had found a lot and wanted to build an energy efficient house, I was ecstatic. Here was my chance to prove that with good design, you could build a very energy efficient, passive solar home at a reasonable cost, and so the design process began. Working together we came up with a house that meets all of her needs while reducing energy needs and costs while using as much solar energy as is reasonably possible.
When I design a building I use a whole house method to make decisions, taking into account the added value and costs. It's kind of hard to explain, but many of the choices we make in the design phase will have an impact on not only the energy usage of the house, but also the costs as well. I have a unique advantage over most Architects, in that I don't just design the building but I also build it. I know how much in cost to build things and how the cost of materials and labor can be reduced through good design. Here are a few questions I ask myself when making decisions about design or materials, first: Does this save energy? Saving energy always saves money the next question is how much energy does it save? How much more does it cost, if it cost more? Is it better for the environment? Will it last longer? Is it produced or available locally? So, here is the list and some information about the advantages and disadvantages of each, most have overlapping advantages that work together to save energy and costs. I know I don't have enough time to cover all of it in this post, but I will continue it into others, when time allows.


Insulated slab on grade foundation

The insulated slab on grade foundation allows us to use the foundation as the heating distribution system for the house. It also has thermal mass properties that allow it to store thermal energy, and regulate the temperature fluctuations of the house. The floor controls the temperature in the house, if the floor is cold the house will be cold, if it is warm the house will be warm. By using radiant tubing embedded in the floor we can deliver heat to the house at a much lower temperature than with traditional heating systems, even better that most radiant systems, that are installed below the floor. The least expensive way to install radiant tubing. The slab only requires the heating system to provide 90F water for heating, under wooden floor radiant requires at least 130F water and forced hot water system require around 160-180F. The lower temperature needed for heating also increases the efficiency of the geothermal heat pump, another whole feature of the house that I will explain in another post. We are also using the foundation as the finish floor for most of the house. When the foundation was poured, we had the concrete guys finish the concrete slab just like you would a concrete floor, polished to a smooth surface. We then covered the floor during construction to protect it from the likes of the plasterers that would make the clean up a nightmare. The finish will be an acid stain with a sealer that will appear much like tile. We cut grout lines into the concrete making it look like a 18"x18" tile pattern, then the acid stain will be applied, neutralized, sealed and then waxed. Once completed it will appear as tiles, but no materials were shipped from afar and did I mention that the concrete used contained 20% fly ash, a waste product from local coal burning plants? No VOC's in the finishing product's.
The cost to do this is comparable to conventional flooring but most of the cost is in labor, making it better for me, not so good for the flooring suppliers, oh yea no waste from left over flooring materials.
So this is just one feature of the house that contributes to the green design, I will list more later things like how we reduce electrical and water demands through appliances and even some strategies to reduce vampire loads. How natural light is used to reduce need for lighting and how ventilation can be used to improve indoor air quality and energy use. How more insulation and reduced air infiltration can reduce the need for heat and add to comfort. How passive and active solar energy is incorporated into the design, that has the potential to make this a true zero-energy home. For me these things seem simple but trying to explain how all of the individual decisions made while designing a house, and all of the choices made regarding materials contribute to the energy and cost of building, is much harder to explain in writing. Here is a quick list of other features of the house.

Whole house design
Oriented for solar
Structural Insulated Panels
Heat recovery ventilation
geothermal heat pump
thermal mass windows
energy efficient appliances
HP adaptable
passive solar
active solar
recycled materials
durable materials lasting longer than 30yrs
low maintenance
water reducing elements
electrical reducing strategies
PV ready with electrical conduits run

I am sure I have skipped over some but I will continue this at a later date with more explanation of all of these features and pictures as well. Stay tuned.

Tom

Passive Solar house: The proof is in the pudding

When I last posted here the weather outside was getting pretty cold and the house I am working on still had no heat. Well we still don't have our heating system up and running yet and the house is maintaining pretty comfortable temperatures. THE LOWEST INSIDE TEMPERATURE EXPERIENCED WAS 41.9F WITH NO HEAT AND A LOW OF -4.5F

We experienced some pretty cold weather over the last few weeks and the house hasn't dropped by that much. The coldest inside temperature reached was 41.9F, that only after 3 cloudy days, highs in the lower 20's and low's at or below zero, with the lowest temp of -4.5F.
Two consecutive sunny days and the house is back up into the mid fifty's during the day and night time lows in the upper 40's. I shot some video when the temps went down to the lowest, I just haven't had the time to edit and post the vid's yet. I'll get to it soon, it is kind of tough to edit the video down to a 10min length, when I seem to be a bit long winded, I'll have to break it into 2 video's.
So, here we are in late January with no heating system installed in the house and I'm not really worried. I was early on, but once I saw how well the house performed under unusually cold conditions, I'm not worried about the pipes freezing. Hopefully the heating guy will show up tomorrow, it is starting to hold up progress on the job. Not that we need heat to work in the house but some of our finishing products need 60F heat just to work. We still have some work to finish on the inside like the interior doors and baseboard, cabinets installed, finish plumbing and the floors.
The floors are being finished with an acid stain concrete and we have been preparing them over the last few days. If you have never seen an acid stained concrete floor you might be surprised at how they look. I'll post some pictures as we complete the floors I think you will be pleasantly surprised at how warm and attractive they are. It's not just about the look, it's also about the energy. By using this finish for the floor, we add no resistance to the heat radiating from the floor. With no resistance we can lower the water temperature we need to heat the house. In turn this makes the geothermal heat pump work more efficiently and lowers the heating bill even further. This is where architectural design meets engineering in house planning, when these two work together the result is not only attractive but functional as well.

What is it that lets this house stay so warm, without heat, when it's so cold outside? There are a couple of things that are key, the insulation, the orientation, the thermal mass windows and the air sealing. Those 4 things when thought about carefully in the design phase and executed in the construction phase have enabled this house to almost heat itself. Not quite but with a very efficient heating system, maybe some solar panels and the use of geothermal energy the energy bills will be much lower than I originally expected. I originally thought the heating for this house would cost around $700 annually, but after seeing how well the house maintains without any heat, I am convinced that it will be at least 25-30% less than expected. We will see, I will be monitoring the house over the next few years and see just how much energy the house uses annually.
THE PROOF WILL BE IN THE PUDDING.

Tom Pittsley
ecobuilder@aol.com
www.eebt.org

Passive solar works, just how well we are about to find out.

No heat and we haven't frozen yet.

So, the passive solar home I am building is about to be tested by mother nature. With some of the coldest weather we have seen in several years approaching and still no heating system installed. Well, I quess you could call the Thermal mass windows a heating system.

We shall see how well the house is insulated because this is about to happen. Although we have experienced some very cold nights and days, the cold that is predicted will be 4-5 days with lows around zero and highs in the upper teens and very limited sun. How cold do you think
the temperature in this unheated house will get??
Take a quess!
I predict the lowest temperature the house will experience will be no lower the 38F. not a best case senario, but not bad for a home in New England with no heat.

I will post a video of how the house performs and lets see how well the Sturctural Insulate envelope works

Here is a video showing how well the house performed on
January 1,2009 with no heat in the house and
a night time low of 4.5F