Deep Winter Greenhouse
Creating a sustainable growing space in colder climates.
Some of you might be wondering, what exactly is a Deep Winter Greenhouse (DWG)? In a very condensed description, it is a passive-solar greenhouse that is specifically designed to be economical and sustainable while running through the cold winter seasons of the higher latitudes.
The Deep Winter Greenhouse is a great solution to any region with a short growing season. Taking advantage of passive thermal strategies, a DWG allows growers to produce greens throughout the harsh winters, satisfying the need for year-round fresh produce with minimal energy consumption. Building on the work of Dan Handeen at the University of Minnesota’s Center for Sustainable Building Research, this model incorporates sustainable material strategies aimed at further reducing the greenhouse’s energy footprint. In addition to actively growing produce, this greenhouse serves as an educational tool for the next generation of farmers and gardeners.
Let’s Start at the Beginning
Greenhouses historically have been used as glass structures that create an environment for plants, usually a specific crop in a specific season. This environment is designed to be ideal for the growth and production of the specific plant being tended.
Home environments are typically hobby size and used to ‘jump start’ the growing season in the spring with germinated plants and seedlings. These small houses are sometimes not economical to operate more intensive growing cycles during deep winter, as they are not energy efficient and heating the costs would be prohibitive.
How Deep Winter Greenhouses Work
This revolutionary concept in greenhouse design uses heat from the sun (with a south exposure) and the storage capacity of the earth (by moving air into and out of the earth) to keep a greenhouse producing even in the coldest of winter months.
The design of the greenhouse is different than a ‘normal’ glasshouse. The design of this DWG has its primary glass only on the south side. The wall is very steep and has a pitch of 60°, which is very steep.
Ideally, the north side may be earth sheltered, as in a ‘walkout’ design. Reflective surfaces may be used on interior walls to further capture sunlight and move it to all areas of the growing greenhouse.
Also, in our ideal greenhouse, blinds (shades) will be installed and they will assist the nighttime retention of heat in the environment, but also in the summer, they will help keep temperatures from becoming excessive.
The real center of this ‘system’ is the earth underneath the DWG. The earth below the greenhouse is a ‘heat sink’ or often called an ‘earth battery’. This method of using the earth is called by many ‘Ground to air Heat Transfer’ or simply GAHT. It is not geothermal by definition and does not use a compressor to transfer ground temperature. It is a much more simplified system.
This is an overly simplified description of the system, and there is much more that goes into the building of a system like this but gives one the general idea.
Sustainable by Design
Every single human relies on this planet of ours to create stable living conditions, and part of the issues facing our world right now is due to our dependence on fossil fuels. Every step we can take to move to more sustainable sources of energy only benefits us all in the long run.
DWGs are the perfect way to sync up our desire to rely less on fossil fuels, with our desire to have easy access to local, organic, and unprocessed food. The ultimate goal of the DWG is to reach a point of energy net zero. This means no additional energy is required to operate the structure, even through a northern winter! This is an incredible goal, but achievable.
A few solar collectors can assist with the operation of the fans and small electronics. A storage battery can be greatly beneficial for the operation of electrical at night, but backup electrical and heat must also be considered in extreme northern locations.
There are many things to consider when it comes to these types of structures, but we are here to help answer any questions, or build you your own Deep Winter Greenhouse! Just contact us today to start discussing it.
We have brought together a collaboration of highly skilled and experienced individuals to work together to produce a DWG for the University of Minnesota Landscape Arboretum. This top level, awarded winning education facility near Minneapolis is over 1000 acres of research and education to the eager gardeners of Minnesota and throughout the world.