Archive Monthly Archives: March 2011

Passive House Example Up the Coast

Here is a brilliant video that show many details of the passive house construction.  It’s an affordable housing project near Point Reyes, about 100 miles up the coast from us.  Our project is a little different because it’s a remodel and not a new construction.  Still the passive house approach to insulation, airtight building, HRV and windows are all relevant for us.

Grab a cup of tea and enjoy this 30 minute video.

Rain and Drain

“Talk to everyone and ask them what they know…” was one of the advice we received recently.  This paid off in our quest for water solution.  The water problems we are addressing, in order of priority, are:

  1. Reduce moisture in the crawlspace under the house.  Moisture/water is essential for mold growth and during the rainy season the mold spores are happily multiplying under the house.  Because the house is not tightly sealed the smell of mold is present in the house during the rainy season.  My mother told me I developed asthma as a toddler living in a moldy house.  So, dry crawlspace means less mold and healthier indoor air quality. 
  2. Keep rainwater away from the house.  Directing the water away from the house will help keep the crawlspace drier and keep the house structure drier.  On one of the photos we saw from the house inspection was signs of water on the wooden posts under the house.  We want to prevent rot and keep the structure healthy too.
  3. Recharge the groundwater on the property.  Sending it down the storm drain alleviates our problem at the house but it still may contribute to erosion and depending on what is carried by the water from our property (e.g. asphalt bits from the roof, residual pesticides on landscaping, etc.) it may contribute to water quality issues.

We know from talking to our neighbors that there is good chunk of clay under the topsoil that prevents water from draining nicely.  It will eventually drain, but this is very slow.  Our neighbors have multiple sump pumps to drain the excess rainwater on their property to the storm drain. 

Getting a soils report done is quite expensive so we followed up on an idea that was mentioned by a contractor who installs solar panel.  He said, “Why not go through the yellow pages under septic system installation and ask them if they’ve done vertical leech field for water drainage purpose around the westside?”  Hmm… interesting thought.  That would be great way to find out about the geology and soils condition.  We would not have thought about talking to the septic people since we’re connected to the city sewer, but the application makes sense.  So I flipped the yellow pages and rattled off the phone numbers while Kurt spoke with them.  We ended up having Darryl from Battle Mountain Excavation dig a monitoring hole using a hand auger and installing a 2 inch PVC pipe for monitoring.

So what are we monitoring?  Well, we learned that just because you hit sand below the clay, it doesn’t mean that the rain water will simply drain into the sand.  Apparently there could be different water dynamics going on at different levels.  One way to measure how quickly the layer below the clay absorbs water is to put in a monitoring hole using a PVC pipe that is perforated on the bottom then sealing the top with clay to isolate the water level activity happening at the lower level.

The drilling work done by Darryl and his crew was informative. Basically there is good topsoil for the first 16″ then there is dark clay, followed by lighter color clay and finally sand.

Cross section diagram of the monitoring hole

The pipe is capped at the top to prevent rain from getting in.  Periodically we will measure the water level beneath the clay layer by dropping a tape measure with a float at the end to read the depth.

Dark color clay like this is beneath the topsoil.  Goes down to about 43 inches.

Then it changes to lighter color clay and goes down until 8 feet.

So, if we determine that the water level below the clay has capacity to absorb water during/after storms then we’ll likely have a french drain or a swale created in the backyard for drainage.

Also, if we have to pump the rain water to the storm drain we found out that it’s not so bad.  We talked to Dave Reid, a fellow water enthusiast with geology background and learned that there is a public online application that map the storm drain flows.  We used this to find out where the storm water went.  Here’s the link to this GIS mapping tool –

Storm water from our area goes to Neary Lagoon, a wetland in middle of the city next to the water treatment facility.  This wetland is a habitat for various wildlife, including the fish, Sacramento suckers that graze the bottom like vacuum cleaners.  They suck up layer of algae, invertebrates and bacteria.