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Energy Efficiency through the Passive House Design

Posted by Jessica Johnston
Jessica Johnston
Jessica Johnston has not set their biography yet
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on Saturday, 05 May 2012
in Green Building

On April 19th, Lydia and I took a tour of the Midori House being built here in Santa Cruz. This house (which is currently under construction) utilizes the principles of the Passive House design to create an extremely energy efficient home. Passive Houses are designed to minimize heating and cooling needs by creating a virtually airtight structure and utilizing alternative energy sources to create a “Net Zero” structure. Passive structures all share the same core design elements, outlined here in a virtual tour of the Midori Passive House.

Passiv Haus

The Project

Chie and Kurt purchased the 1922 Craftsman bungalow with the intent of converting it into an extremely energy efficient home without having to actually tear the whole house down. As Chie put it, “It is analogous to taking a 90 year old person, keeping the skeleton, but putting in a new respiratory system, a new circulatory system, and giving them new skin and clothes.” With the help of Santa Cruz Green Builders, the homeowners plan to redesign the house into a Passive House while still maintaining the original craftsman architectural style of the neighborhood.

The Passive House Planning Package (PHPP)

Our tour began in the front yard with Kurt, Chie, and Taylor (of Santa Cruz Green Builders) explaining the concepts of a Passive House. It all begins with the PHPP, a special software used in the development and planning of Passive Houses. The software maps climate data specific to the location of the property and incorporates natural components such as the distribution and intensity of sunlight throughout the year (where to put windows on which walls), the climate patterns throughout the year (which days require cooling or heating), and the surrounding air quality (to determine comfort and air quality specifications for the interior of the house).

Construction: A Super-Airtight Envelope

Airtightness is essential to the Passive House model. In order to test airtightness, a Blower Door Test is used to measure the structure’s ability to maintain pressurization. For Passive House specifications, at 50 Pascals of pressure the house should have less than .6 air changes (air leakage) per hour. In comparison, a typical house has 7-12 air changes per hour, while the original Midori House had 25. Superb airtightness was achieved through excessive calking of the walls, floor, ceiling, everything. Standard constructions usually do not put this much attention into calking, but for a Passive House this is essential. The windows jut out of the walls to allow insulation to be placed around them, and rigid foam insulation runs continuously along the entire bottom and ceiling of the house.

Passive House PrinciplesThe Heat Recovery Ventilator: The “Central Respiratory System”

You may wonder, if air cannot leak in and out of the house how does the air get circulated? This necessitates the Passive House’s second key element: The Heat (or Energy) Recovery Ventilator (HRV). This device, located at the heart of the Midori House, removes exhaust air and circulates fresh air to all the rooms of the house, transferring energy from the outgoing air to the incoming air. This system is 85-95% efficient at this direct heat transfer, and also utilizes solar thermal energy to make up additional heating needs. With this system, air quality in the home is maintained and heating/cooling costs are reduced.

Advanced Windows

Windows are crucial when constructing a Passive House. The Midori House windows are triple-pane with 6 different kinds of coatings to reflect and retain heat, managing the interaction of infrared and visible light. The specific coating is dependent on which wall the window is placed, determined by the sunlight patterns mapped in the PHPP. The southern facing wall has the highest solar heat gain; therefore, most of the windows are along this wall. Awnings are used to shade the windows in the summer months but allow in light from the low-sitting sun during the winter months.

Efficient Systems: Plumbing

One technique in creating an efficient structure is to assess the hot water demand for every plumbing feature in the home (every sink, toilet, shower, etc.), and instead of applying a one-size-fits-all plumbing system, install high efficiency low-flow pipes that minimize the time it takes to wait for hot water. The plumbing system in the Midori house relies on solar panels to heat up water (with a backup generator for cloudy days), and super-insulated pipes to minimize water waste. Another feature of the Midori House plumbing system is the use of greywater, a technique used to minimize potable municipal water waste. Water from the washing machine can be used for landscaping, while a rainwater catchment system in the backyard supplies cold water for the washing machine and toilets.

Efficient Systems: Fun with Numbers

The Passive House design stresses the concept of energy efficient systems in the home aside from plumbing. These are quantified in many ways, particularly the R-Factor or R-Value. The R-Factor is a measure of the heat retention, or resistance to heat transfer, of a substance. For example, wood, a very poor insulator, has an R-Factor of 1 (designated as R1), while the insulation used for the hot water pipes has a factor of R5. Rockwool (a rigid insulator) encapsulates the entire walls of the Midori house, reducing thermal bridging that occurs due to the poor insulation of wood. The walls, therefore, are R26, compared to R13 for standard walls. The home also boasts ceilings with R40, and floors with R25.

Shown below: heat loss before and after Passive House retrofit.

Heat Leakage Pre-Passive House Retrofit

Heat Leakage Post-Passive House Retrofit

Materials Sourcing, Recycling, and Repurposing

It would seem counterintuitive to construct an energy efficient home using very un-green construction methods. Kurt, Chie, and the Santa Cruz Green Builders made it a point to recycle and repurpose as much of the waste material as possible. Wood removed from the site was recycled. The exterior siding is made from recycled cement fiber. The interior of the house is insulated with cellulose (recycled newspapers). The special windows were imported from Canada to reduce the carbon impact of transport.


Our tour ended in the backyard, where Kurt and Taylor made their final comments about green building practices. The key to the Passive House approach is biomimicry, particularly solar heat gain, efficiency, and energy storage. In the average American home, heating water is the biggest energy guzzler, following by air heating, appliances and lights. Occupant behavior is what ultimately makes the difference. You can have the greenest house in the world, but it will not matter if the occupant does not live a green lifestyle.  Proponents of green building design wish to move society toward a “Net Zero” model, curbing our global impact on the environment.


Sources :

 Passiv Haus Institute

 Passiv Haus Alliance

 Midori House Blog

Santa Cruz Green Builders

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Pure. Organic. Mattress.

Posted by Jason
Jason has not set their biography yet
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on Tuesday, 01 May 2012
in greenspace

Your bedroom is a sacred place – the space where you rest, relax and recharge your body after a hard day's work. It should be a safe environment, free of worry and health hazards; however, most of the indoor air pollution stems from products we bring into our own homes. I can think of few products that we are more intimate with than our mattress. Did you know that many of the materials and chemicals used to manufacture and fire-proof mattresses are toxic to the human body? With so many conventional and “natural” or “hypoallergenic” mattresses to choose from it can be difficult to decide what to purchase. After all, we spend roughly one third of our lives rejuvenating in the comfort of our own bed.  At greenspace, we take your health seriously, which is why we source all of our mattresses from Organic Mattresses Incorporated (OMI), an industry leader in providing consumers pure organic beds.

The Bad. The Good. And the Ugly.

FloraThe popularity of synthetic rubber and foam in mattresses comes as no surprise. Companies are able to cut their production costs by utilizing petroleum-based materials instead of natural ones and can pass on these cost savings to the consumer. Many mattresses employ a polyurethane foam encased in vinyl covers, which are also treated with boric acid (roach killer), arsenic, or other toxic flame retardants. Every one of these materials can be harmful to the human body, especially to infants and children. Our mattresses employ the amazing properties of wool for comfort, as a natural thermo-regulator, as well as for the only flame-retardant needed. Because wool is hair, it doesn’t support combustion.

Sleep at Peace

Everyone has to weigh the short-term cost-savings at the time of purchase - with the potential longer-term health costs of breathing toxic chemicals while in bed. If you are a chemically sensitive person or simply trying to avoid the added health risk of welcoming in dangerous substances, we feel it’s worth a careful consideration of OMI beds.
Rubber Tree Latex Tap
A mattress is a significant investment in your well-being. OMI embraces this like no other mattress company we know of, by making all of their beds with quality, durable and eco-friendly materials. Natural rubber latex, American grown, organic cotton and premium eco-wool is all they choose to put into their beds (which they manufacture in Northern California). But don't just take my word for it – link to OMI's website and you'll see they have nothing to hide about their products. Did I mention they offer an industry leading 20-year warranty on their mattresses?

Once you're ready to sleep comfortably and chemical free, come into greenspace and try out a few of OMI's mattress models. And make sure to ask us about the latest sales from OMI. They happen often.


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The Message is in the Bottle: The Truth About Bottled Water

Posted by Jessica Johnston
Jessica Johnston
Jessica Johnston has not set their biography yet
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on Wednesday, 18 April 2012
in Green Living

Plastic Bottles awaiting recyclingAmericans are always on the go. Between home, school, work, and play, our rapid lifestyles make portable and pre-packaged goods very appealing. The bottled water industry’s success is a direct exploit of this notion of necessity and convenience. But while bottled water may seem like the answer to our need for water-on-the-go, like everything else, there is a catch. A pretty big catch, at that: Roughly 17 million barrels of oil are used in the production of water bottles (including manufacturing and transport) each year. Bottles that are not recycled contribute to the over 3 billion pounds of waste that end up in landfills (and fun fact: plastic takes about 700 years to break down, so those 3 billion pounds of waste will be sticking around for quite a while).

Do single-use water bottles still sound appealing? Maybe so. The industry has done a good job of convincing the public that bottled water is cleaner and safer than tap water. And at face value that would make sense. Of course the water bottled from majestic mountain sources is going to be fresher than the water coming out of my dirty kitchen sink, right? Actually, what many people don’t know is that over 40% of bottled water is bottled from municipal water sources. That’s a fancy way of saying almost half of bottled water on the market is bottled tap water. Another little known fact about bottled vs. tap water? Bottled water is considered a consumer good and therefore regulated under the Food and Drug Administration (FDA), while tap water, a public good, is regulated by the Environmental Protection Agency (EPA). Consequently, tap water, despite the public opinion of being more contaminated and unsafe, actually has stricter regulations for health and safety than bottled water does. So, in fact, tap water is safer than bottled water.

Klean Kanteen ColorsStill not convinced? Maybe consult your pocketbook. In 2009, Americans spent $10.6 billion on bottled water, almost 1,000 times the cost of tap water (ouch!). Still, many will claim that the convenience outweighs the cost. But there are many environmentally friendly options out there, such as refillable/reusable water bottles, which conveniently provide you with the same water you would otherwise be paying for, at a fraction of the cost.

greenspace offers many options for sustainable alternatives to single-use water bottles and other disposable goods. Klean Kanteen products, for example, are a convenient, affordable, stylish, and more environmentally friendly way to drink water. You can make a difference (and even save a buck!) by limiting your purchases of plastic water bottles, reusing and recycling the ones you do use, and buying a refillable water bottle to take with you when you are on the go.



To learn more about bottled water, check out these sources:


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Energy Modeling for Building Design and Construction

Posted by Jason
Jason has not set their biography yet
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on Wednesday, 11 April 2012
in Green Building

On Wednesday, April 4th, I spent the evening among architects, builders, engineers and students listening to an inspiring presentation on energy modeling for integrated building design, planning and construction hosted by the US Green Building Council's northern California chapter at the Monterey Bay branch. It was a thorough overview of what energy modeling entails when planning a new building, or retrofitting an existing one, how the design process is implemented to ensure maximum efficiency and minimal sticker shock, and incentives for developers and builders to meet higher standards of energy efficiency. Using case studies including the Nordic Naturals Watsonville warehouse and the Midori Passiv Haus, built right here in Santa Cruz county, the presenters demonstrated how utilizing an integrated design and planning team to realize clear goals from the beginning, lead to the highest efficiency, most cost-efficient result for the developer.Midori Passiv Haus

One perceived barrier is that these types of projects are too expensive to attempt. However, free and low-cost energy modeling software is available to assist users in accurately identifying the most feasible energy saving strategies to implement in a new project or remodel. It is even possible to design buildings that consume less energy to light, heat and cool simply by taking passive solar orientation into account. Furthermore, the better a project is designed and built to exceed energy codes, the shorter the return on investment period is on upfront costs for the homeowner or developer. Finally, greenspace is your place to find finishes to complete your project with sustainable quality.

While benefits for developers and homeowners are essentially “built-in” to energy efficient homes, generous incentives are now in place for residential builders to exceed California energy code so that both builders and residents can gain from superior energy efficient houses. The lesson of the evening was that, with proper planning, it is now easier and more affordable to construct extremely efficient commercial and residential buildings.


California Advanced Homes Program

U.S. Green Building Council Northern California Chapter

Bright Green Strategies

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What IS Linoleum?

Posted by Jason
Jason has not set their biography yet
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on Tuesday, 03 April 2012
in Materials
What Is linoleum, anyway?
Marmoleum Kitchen
It’s that plastic stuff on the laundry room, kitchen or bathroom floor, right? Nope. That’s vinyl. PVC, aka Vinyl, is one material greenies agree should be removed from the built environment altogether. Every step of it’s life, from manufacture to disposal, is toxic. The more flexible (soft) it is, the more VOC's it contains. It never stops outgassing either. YIKES!

So here’s one awesome alternative: linoleum. It’s been around for a very long time, and it’s a 40 year floor, with gorgeous color that goes all the way through. It’s made from linseed oil, wood flour, cork, mineral pigments and has a jute backing. These properties mean that it’s a biodegradable, naturally anti-microbial, resilient, sheet good that looks great in kitchens, bathrooms and laundry rooms and beyond. The ant-static properties make it easy to clean, reduces exposure to allergens and can improve indoor air quality. The baby and animals can crawl around on it without you worrying about what they are breathing in, too. And, at around $4.50 per square foot, we can afford it!

Linoleum is also great for countertops (very retro!) and makes an excellent desktop material as well.  Come by greenspace and you can check out our office desks featuring linoleum tops (Forbo Marmoleum glued to wheatboard)

Drawbacks? TheMarmoleum Click tiles and floating floor options are do-able for DIYers, but the sheet goods (69 inches wide) are more cantankerous, need to be installed by a trained professional, especially because the material grows a bit in one direction and shrinks in the other. It’s all made in Europe, so there is embodied energy in the freight involved to get it to the U.S. Also, some folks are sensitive to the natural linseed oil odor, so it’s best for them to experience limited exposure to a sample before installation, and perhaps wait a few days before occupying the space.

We source from two suppliers: Armstrong and Forbo. Forbo has coined a new term by calling its natural linoleum Marmoleum, the same way we’ve come to call facial tissue Kleenex: that’s successful branding!
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Cork Flooring: Beautiful, Durable & Sustainable

Posted by Jason
Jason has not set their biography yet
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on Wednesday, 21 March 2012
in Materials

Cork Flooring - US Floors AlmadaCork has always conjured up images of timeless ecological flooring - perhaps because I personally grew up with it – but also because cork may be one of the flooring industry’s silver bullets due to its beauty, function and affordability for our customers. On a microscopic level, cork mainly consists of air, making it easy on joints as well as a wonderful acoustic and thermal insulator. In truth, cork is highly compressed before it can become flooring, so it retains the ability to reflect your body heat back to you (feels warm underfoot), but gains resilience, in terms of recovering after being scratched. It also has natural mold, fire and insect resistant properties. Furthermore, cork flooring meets Greenguard’s strictest indoor air quality standards. The manufacturers of cork flooring products that greenspace sources are reputable companies who add several layers of a very low-VOC urethane finish, ensuring a durable floor. Cork’s natural beauty shines through in every style, with majestic patterns and enough color options to suit any scheme. Finally, cork flooring is an affordable option both in material and labor costs. We carry click plank floating floor, glue-down tiles, as well as circular cork mosaic tiles. The floating floor style is especially easy to install for a professional and straightforward for an advanced DIY’er.

Is the cork oak endangered? 

Portugese Cork OakAt greenspace, we absolutely love cork, so when we heard rumors that cork trees were disappearing, we were curious about how that could have happened to these forests, since cork has been successfully harvested for a variety of applications for hundreds of years. To embrace this miraculous material, we needed to understand a common myth surrounding the eradication of the cork oak forests.
While cork has been championed by wine-makers for hundreds of years, it has not been until recently that cork forests have been labeled threatened. Over many centuries, harvesters along the Iberian Peninsula and North Africa have perfected the technique of removing outer bark tissue from the tree every nine to eleven years without shortening its lifespan. This fostered a mutually beneficial relationship between trees essential to a delicate ecosystem and a sustainable local economy. The cork oak tree itself is extremely valuable to the natural ecosystem because it harbors animals, pumps nutrients into largely poor quality soil, and even captures a vast amount of carbon dioxide from the atmosphere. So what happened to these forests recently to warrant such a grim outlook?

Cork Bark CloseupWidespread adoption of synthetic bottle stoppers and screw-top caps have shrunk the demand for cork so that land previously used to grow and harvest cork forests has either been left fallow or been converted to grow other varieties of crops. The lessening demand for cork is the main reason behind the rumor of vanishing cork oak trees, which means that when we purchase cork products, we help cork forests thrive. Not only is this good news for wine connoisseurs, but also for advocates of cork flooring, since cork flooring is actually made from the post-industrial by-product of the wine bottle stopper industry! This alone makes it one of the most eco-friendly flooring options available.

The idea of plastic bottle stoppers adding to the ocean gyres and clogging the digestive tracts of Albatross makes us want to move back towards corks anyway!

Unexpected durability & versatility

US Floors - Natural CorkCork proves itself time and again with its versatility in blending with and enhancing existing finishes. Many times, folks come to greenspace looking to replace carpeting in areas adjacent to hardwood floors, but they want something different from what they already have. Often, the new floor is going right up to existing oak flooring. I find this a little ironic, because cork comes from the oak tree, but the patterns of cork are often organic, rather than linear, yet the colors can blend well with oak, alder, cherry, walnut and many other hardwood species.

Many people like the idea of working on cork in a kitchen, but are worried about water damage. If you want it to be worry-free, a final coat or two of finish can be applied after the installation to help delay water infiltration. Bear in mind that standing water will ruin almost any floor, however, if it goes unnoticed (you are on vacation) for some time.

Cork’s superior properties as a fabric and building finish material make it suitable for many uses aside from flooring and wine bottle stoppers. At greenspace, we carry products that employ cork for furniture, backing for cutting boards for a sturdy grip on countertops, bowls, bibs for babies, and high quality underlayment for many types of flooring. The versatility of cork and unparalleled function will ensure its use in many future applications.

Check out these websites for a bit more about cork and cork flooring:

US Floors - usfloorsllc.com
Nova Distinctive Floors - novafloorings.com
Portugese Cork Association - apcor.pt

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