Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.

We have a small 1940s single level house (1005sqf) in Berkeley, California that is in need of a deep energy upgrade. Our plans include making the envelope air-tight, increase insulation, make use of solar orientation by changing the interior layout and exterior glazing. The kitchen and bathroom also need to be upgraded, along with the electric wiring and plumbing. Yet, the foundation is good and so is the roof. We like the location, which allows us to walk everywhere and enjoy the mixed use neighborhood. The best part is our garden and open space that we love.

Now the question: How might we do this affordably? We have a limited budget and it is even made smaller due to the very high construction and remodeling cost in the Bay Area. We are ready to put in our own sweat labor but how do we find people who would like to work with us? Any other hints, tips, suggestions etc that would also be helpful to others in similar circumstances.

Many thanks,

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Hi Kaushal,

First step is to understand where you are in terms of energy costs.  If current energy costs are low, then there is little to save.  Also, knowing current costs helps you measure improvements, was the job done correctly.

Do you have some energy history on the building? 

Wall thickness, insulation levels, furnace, boiler, air conditioner, location of these, age, efficiency.

Be cautious of claims from mfgs and sales people who state their product will reduce your costs by 50% or anything like that.  Ultimate savings are a combination of more than one improvement and often one fix will reduce the savings potential from another.  Savings from new windows is often overstated.

CA may have some incentive money and in some cases if you do half of the work yourself before being evaluated, the remaining half may not qualify for the government money.  I'm about as far away from CA as one can get in the states so I don't keep up on what you folks are doing out there.

You use the term "deep energy retrofit" and then you say your budget is limited.  Those two statements don't go together.  An extensive upgrade cannot be done on limited funds (in my experience).  However, if you determine that $20,000 in improvements will save you $4,000 a year then that is something you can take to the bank, or PACE program, where financing costs (low interest rates) can provide the needed funds.

Start at the top with determining your current numbers and collecting the many details about your house.  There are DIY audit programs you can use to help.




There was a deep energy retrofit upgrade project (to Passive House standards) in San Jose posted on these boards not too long ago and the home owners decided to do the retrofit for the same reasons you state. You could contact their architect or general contractor to see how "affordable" this would be for you. Generally speaking, a project of this intensity involves a complete gut/rehab (or exterior strip/rehab or both), engineering studies/work on the change to interior walls, local zoning board meetings/proposals/modifications, completely new HVAC/heat recovery ventilation system/domestic hot water system/high performance windows/high performance exterior doors as well as insulation, rain drain systems, air barriers. Maybe somewhere on the order of $400+ per square foot of finished space. As Bud Poll commented, it may be far more "affordable" to do an interior re-engineering and a partial/cost-effective energy retrofit.

Hi David & Bud,

$400/sqf > $300 sqf. The latter is the minimum cost of new construction in the bay area. Deep energy upgrade/Passive house retrofit should not cost more than building a new house.  If it did than passive house remodel will simply not be cost-effective nor affordable for most. I reject these high costs and I do it not only on the basis of optimism alone but rather on figures from successful passive house retrofits around the country, which have happened for much much less. Yes, granted that in general labor is immensely more expensive in the bay area, but I treat it as an opportunity for able and knowledgeable homeowners (and their family/friends etc) to put in their own sweat labor to partially offset the higher costs. 

It is my goal to show that a passive house retrofit can be affordable even in the bay area. To this end, I invite generosity of people in this community to share their knowledge and experiences that will help me and others similarly disposed to make it happen. I believe good planning and design can also go a long way in offsetting the costs. So I welcome hearing from folks who have gone through passive house retrofits themselves and share with us their lessons on what worked and what could have worked better. 

I take it that if we are serious about our environment, energy reduction etc, these concerns do not end with the boundaries of our homes but it matters significantly that our neighbors do the same. And what better way to inspire others to follow suit than sharing our knowledge and expertise. I want to acknowledge Chie and Kurt of Santa Cruz, CA. (check their bolt: midorihaus) for doing just that. I would love to see more doing the same.

Thank you,


I mis-spoke - I was referring to the Midori House in Santa Cruz. Have an in-depth discussion with the owners to see what their total cost-per-square-foot ended up. There is the cost of deconstruction (labor, alternative residence costs, disposal, etc.) and any structural repair (as in the case with the Midori House) in addition to any re-engineering (engineering/architectural fees, permitting, etc.) and the advanced re-construction costs which are significantly higher than typical "code-built" homes (much more expensive components, iterative testing, specific training/experience needed, etc.). So if you are already admitting that "code-built" new housing costs are roughly $300/sq ft, do not be surprised by the higher cost of a deep-energy retrofit. But if you are looking at living in an area where new construction lots are rare and very expensive, a retrofit may be the only other alternative to looking at a different location.

More food for thought on this subject - read this (fairly) recent blog by one of the most respected authors today about deep energy retrofits: Green Building Advisor - Deep Energy Retrofits

Hi David,

Thanks for pointing out Martin Holiday's article. I do not wish to engage in the debate whether passive house/deep energy retrofits are affordable or not. I already know that they are. You are welcome to read about projects of just this sort. So a better question is if it has already been shown that DER/passive house retrofits are affordable elsewhere, then what are some of the things that can be done (where we happen to live) to ensure that they are likewise affordable here. What I have in mind is discussion of (1) the most economic way to meet the requisite insulation and (2) airtightness in bay area homes? (3) What are some of the most cost effective windows? (4) And similarly HVac systems?

Many thanks!

Plan, plan, plan, plan. The 1st step to is to understand the house, how it's built, the systems, the condition, etc. You need to look at what you want to do, and what needs to be done. You can than come up with options, do some cost estimating, and than try to balance everything and come up with a plan. Most upgrades are undertaken as things fail, or based on a perception of needing done without any plan (my furnace is old & inefficient, etc.).

You can spend a fortune on kitchens & bathrooms. Moving walls can get expensive depending on the structural issues. Adding windows can be expensive in existing walls. Upgrading electrical, plumbing & heating systems can also be fairly big cost items.

How you view costs is important. What's the payback on a more expensive car? (base model vs. fully loaded) all else being equal. If you are adding things you don't have is it the full cost? If you have to add / replace something is it the incremental cost?

Midori house is a great project, but remember, it was a full gut rehab of a house, so much of the cost was not energy related upgrades.

You biggest bang for the buck is airsealing the (existing) house (and duct sealing) as best as you can, insulating the ceiling/roof, walls & floors. This will greatly improve comfort and reduce energy use / cost.

Getting to deeper savings or PassiveHouse levels requires more effort & money, no doubt. PassiveHouse would require an external airbarrier / insulation retrofit at a minimum (Mary James, Butterfly House, Larkspur), or a larger gut / rehab job.

Hi George,

I overlooked an interesting point you made in this post. You said, "Passive House would require an external air barrier". Does this make sense for our climate. From the Passive House institute materials I have been reading, it sats insulation on the outside and air barrier on the inside. I have seen projects that have done this too. I am curious if you can explain why you are proposing the opposite. 



Historically we have done an air barrier on the inside, lot's of intersections, penitrations, discontinuities, easier to damage, etc. Many of us decided that it would be easier to do the air barrier on the outside.

Many still talk about air barriers as being interior and a wind barrier on the exterior (less air tight).

PH requires an air barrier, it can be on the inside or out. Outside is easier, especially in a retrofit.

I've been working on simple thermal upgrades and for collecting heat the roof is a best place short of using a greenhouse wall. How to do this is simple, on the best solar gain roof areas install 1x1 spacers up against the roof sheathing and use 1" or 1-1/4" thick insulation board cut to fit between rafters to create a narrow space to heat with (or cool at night). These should be sealed to make an airtight pathway and you would want to calk joints in the roof sheathing that may leak.

So at the lower end air is allowed to enter and at the top install ducting to pipe this heat to below the floor where any batt insulation is removed and plastic pipes full of water are installed strapped between floor joists for thermal-mass (most will take 3-6" pipes). This is an important and expensive part of the system but by providing the thermal-mass you can store heat when it's available to last between heating cycles. To close the space insulation board is added below the joists so the spaces act like ducting.

The outlet can be directed into rooms, or for better efficiency with another pipe & ducting it can be used as the inlet to the roof heating instead of using outside air, recirculation to me is the best for cold climates or where roof orientation or shading occurs so worth the effort as the cost isn't much more. If you're putting up solar panels they can also be used for thermal collection.

With a blower to move the air and a thermocouple switch when enough heat is available the blower moves the air to below the floor for storage and heating the rooms. The ducting inlets at the roof and outlets under the floor need graduated sizing to equalize the air volume to all rafter or joist runs. In summer this can be run at night to store cold.

Then for walls I've found from thermal modeling a simple way to upgrade existing walls by carefully removing the siding, adding 1-1/2" of insulation board or more depending on exposure to cold or wind, add furring strips to keep condensation from wetting the siding and replace it. The furring also greatly reduces conduction of cold winds into the wall. This about triples the thermal resistance and is easy to do.

The image is a modeling run, outside temp is 20C, inside 0C for simplicity and the change in temperature at the thermometer was 13.6C for the standard wall and with the upgrade 4.1C for a 400-minute run.

Another aspect of doing this is that the existing wall mass becomes thermal-mass for the interior so adds thermal inertia to keep the room in the comfort zone. Hope these ideas are interesting, I should have a 12'x14' cabin with data loggers done this summer to have documented results for both ideas.


After seeing the cost estimates by Glenn, my addition of insulation board under the siding on a 2k-sf home 32'x64' if you did the work yourself is about $1,500 and triples the wall thermal resistance, you can up the sealing by calking the board when applied; embedding the thermal diagram this time:

This is my no calculations half assed energy based  renovation suggestions-

First off, Berkeley is a mild climate, If I lived there I might not even bother with heating.   For a small house a Minisplit heat pump system is a no brainer worst case senario you need to heads.

My initial thought would be to tear off the existing siding- remove windows.  Replace existing windows on south side with high solar gain double pane- argon filled casements. Use the lowest U value windows you can afford on the other 3 sides.   Use window pans.    Remove any house wrap and replace with one of the vapor permeable, fully adhered membranes.  Air seal it from the outside.   Add 3” of stone wool outsulation, Strap it and add new siding.   Blower door test it and fix as many leaks as you can. 

Blow in as much insulation in the attic as will fit depending on the ceiling and what it can handle weight wise  go for about R50- R 70.

Add  2 pairs of Lunos E2’s. for ventilation.  That should be enough for  1000 sf

IF at some later time, you decide to renovate the inside, do further airsealing and use Roxul bats between the studs.






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