Is there a radon risk in Silicon Valley homes?

January is National Radon Action Month. Californians can get a free test kit here


While there are many natural hazards that are commonly discussed in the San Jose area, such as earthquake faults, flood planes, and liquefaction zones, there’s one which comes up frequently on the east coast but is largely ignored here in the Valley of Heart’s Delight. The question is this: is there a radon risk in Silicon Valley  homes?
Radon is a colorless, odorless gas - what is the risk of radon in Silicon Valley homes?

First, though, what is radon?

Per the EPA website, “Radon (chemical symbol Rn) is an odorless, colorless, radioactive gas. It comes from the natural decay of uranium and radium found in nearly all rocks and soils. Radon can move up from the ground into buildings through openings in floors or walls that are in contact with the ground.”

If the idea that a radioactive carcinogenic gas can enter your home or workplace completely unnoticed spooks you, that’s understandable. Thankfully, it is uncommon to find radon at high enough concentrations for concern in Silicon Valley. It’s helpful in that regard that it’s a region with few smokers and few basements, both of which can increase the risk.

That being said, radon can be found all over the world, and similarly, homes high in radon can be found anywhere, though they are more or less common depending on where you are.

So how do you know your radon risk?

Santa Clara County is considered to be a moderate, and not high, radon area. Different geological conditions may make an area more or less prone to high levels of radon gas, though, so even here it is possible to have a radon risk.

The U.S. Environmental Protection Agency (EPA) and the U.S. Geological Survey have mapped by county the average potential radon levels in the area, divided into three zoning (Level 3 being the lowest and Level 1 the highest average measurement zones) for buildings without radon remediation. Santa Clara County is a Zone 2 area per the map linked to above. Check the map at Berkeley Lab Columbia Univeristy Radon Project page. Areas with the greatest risk, and which suggest remediation, are those in Zone 1. The are counties with predicted average indoor radon screening levels greater than 4 pCi/L.

If you would like to check your home’s radon risk levels, there are two tests you can use to measure indoor exposure: a short-term test and a long-term test, and both are affordable. The short-term test only takes a few days, might cost around $15, and is a less reliable way to get results quickly. Long-term measurements take a year and uses detectors placed one on each living level of the house (so approximately $25 for a single-story, $50 for a two-story home). These are much more accurate, so they are the ones preferred by researchers and home owners, but the results will take longer to reach and the cost is higher.

Worst-case-scenario, you have measured 4+ pCi/L (picoCuries per liter of air), the level at which the EPA recommends remediation. Now what? Prepare to spend a few thousand dollars (a great bargain to keep you and your family healthy). The standard treatment involves the installation of a pipeline and fan system which will pull the seeping gas from the ground beneath your house and redirect it outside where it can disperse safely in the air. The only apparent downside to this procedure (other than the time and cost of installation) is that your heat and air conditioning costs may rise slightly. Check with the experts, though, to get the full scope of both the risk and the remediation impact.

Read more at the pages listed below.




The Willow Glen Area of San Jose – Real Estate Market Update

How is the real estate market in the Willow Glen area of San Jose?  There are multiple ways of viewing it – via price point, school district, proximity to “downtown Willow Glen”, by numbers or percentages of distressed sales (sale type), and many more criteria.  Today we’ll look at the broad market numbers for the MLS “area 10” (all of Willow Glen) and at times just the zip code for San Jose 95125, which covers the majority of the Willow Glen area.  This post will only cover houses or “single family homes”, not condominiums or townhomes.

I ran the months of inventory for homes in Willow Glen (our MLS area 10) by sale type.  Here’s what I found – most of the market appears to have about 4.95 months of inventory, with short sales being considerably longer.  (This may have had different results had I isolated certain school areas or price points – this is a “sweeping view” of the area only.) The National Association of Realtors says that less than 6 months is a sellers market, but for our area, this is fairly “cool” and most sellers would not find the market to be all that much in their favor. (Six months is supposed to be a balanced market.)


Willow Glen Months of Inventory by Sale Type May 2011


It is unusual for there to be so little variation in the MOI, so I double checked but this appears correct. Often bank owned homes or REOs fly off the market.  Odd that it’s not happening here, too.

Next, a selection of statistics and trends in the numbers from my REReport for Willow Glen (click on link for more info) – prices here reflect sold prices (median and average), not list prices:


Trends At a GlanceApr 2011Previous MonthYear-over Year
Median Price$675,000$704,500 (-4.2%)$665,000 (+1.5%)
Average Price$710,516$788,240 (-9.9%)$676,773 (+5.0%)
No. of Sales4656 (-17.9%)41 (+12.2%)
Pending Properties8585 (0.0%)114 (-25.4%)
Active183158 (+15.8%)188 (-2.7%)
Sale vs. List Price97.2%96.5% (+0.8%)98.8% (-1.6%)
Days on Market5771 (-19.9%)51 (+11.4%)


Prices appear down from the prior month but up from a year ago.  That’s good news for Willow Glen home owners, who hope that the worst is now behind us.  Days on market are better than the previous month (but worse than a year ago) and inventory is up from last month but almost the same – just a little less – than a year ago.  It’s a mixed bag. (more…)

Househunting in Silicon Valley? Revisit Your Favorites Over & Over Again

Whether you are looking to buy a condo, townhome, patio home, or single family home in Silicon Valley, it’s imperative that you revisit the neighborhood multiple times before deciding to buy (or to complete the purchase). This is an important part of your “due diligance” as a home buyer.

Why revisit so many times? Because certain key things may differ from hour to hour or workday to weekend day:

  • – noise levels
  • – the number of parked cars on the street (few is good, many suggests overcrowding)
  • – neighborhood activity (good or bad: people strolling, walking dogs is a good sign – too many yard sales or other activity may not be a plus)

If you visit on a weekday morning or afternoon, the street could be relatively free of cars and other vehicles, but it might be entirely different on a Friday night or Saturday afternoon.

Conversely, if the neighborhood appears consistently appealing, quiet, well kept, and not overcrowded or loud, that’s something to appreciate as you factor in which home to buy. You can usually remodel your own home, but it’s very difficult to do a makeover on the street where you live – so investigate throroughly before you buy, whether it’s in San Jose, Campbell, Saratoga, or Los Gatos. You will be more sure of your decision and happier with the results if you do your neighborhood homework upfront.