There's a gorgeous Cherry tree in my back yard. In fact, I purchased this particular property in part because of the lush Cherry tree canopy.
I envisioned that eventually, the ADU would sit under the canopy. I imagined that as I lay in bed, I'd look up through a bedroom skylight, through the branches and leaves into the cloudy night sky. During the day, I'd be able to watch birds flying in and out of their 60ft high nested homes.
These visions came to a crashing halt halfway through the design process when I learned that I could not place the ADU under the tree on the south side of the property, for fear that the ADU would either critically damage the roots of the tree, or that the roots of the tree would eventually upend the foundation.
After much deliberation, my architect and I scratched our whole site and ADU design, and made the decision to push the ADU across the yard to the north. This decision totally altered the entire design process, causing my architect to begin again his design again from scratch. This caused a month delay in my design process and $800.
The Cherry tree is now in full bloom. And though my sinuses are suffering dearly as I write this, I can't imagine having cut down that beauty. It would have gone against my other, better senses.
Though the tree is easy on the eyes, let's side that aside. Let's not look not at the beauty of the tree itself; let's just look purely at the fiscal services that the tree will provide.
What is the value of this tree?
Being set due south of the ADU, the 60 ft canopy perfectly blocks out the arc of the summer sun, providing a natural form of air condition due to the shading it provides. Trees can reduce air conditioning demands 20-50%. And, even more directly, when spending time outside, it will actually reduce the increased ambient 'urban heat island effect' temperature by 2-10 degrees in its immediate shading zone.
Here's the arc of the sun, looking at the ADU. As you can see, from the sun's perspective, the ADU is mostly not visible behind the tree, except for a brief spell in mid morning and later in the afternoon.
During the winter, when the foliage has dropped, the lower arc of the sun's gaze should dapple its way past the vacant branches and in through the houses glazed surfaces, warming the darkly colored concrete floors and other thermal massing surfaces in the house. It will marginally offset the need for gas powered heating the house during the winter, at least during daylight hours.
The trees roots cast their way across the lawn, and absorb up to 100 gallons of stormwater daily--which is a significant benefit in a humid climate like this one.
My tree will reduce urban air pollution in my backyard, including: carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, and particulate matter. To be fair, the tree pollen also causes allergies.
And lastly, the tree will reduce stress and increase health. There have been numerous studies on the health effects of trees near hospitals, prisons, and schools, leading to quicker recovery, calmer inmates, and more attentive students. There are also studies on trees' effects on reduced crimes rates and reduced symptoms of ADD.
And, from a purely fiscal perspective, a study in Portland showed that street trees growing in front of or near a house added an average of $8,870 to the sales price. As I mentioned in the the first portion of this post, I purchased this property in part because of the wonderful tree canopy. So, I guess I am playing right into this particular statistic.