Carbon Monoxide, and Naps

It may not be the Turkey that makes you sleepy.

Carbon monoxide from an electric oven

Cooking the turkey for hours can introduce considerable amounts of carbon monoxide to the home during the cooking process.  Turkey has a component that has been attributed to that nap after dinner.  Others hypothesize it is just eating too much that leads to sleepiness.  It is also possible that exposure to Carbon Monoxide is a contributor.

If carbon monoxide is a culprit, it is not only related to gas ovens. 

I am not sure how much CO is given off in an electric oven during the cooking of a turkey, but certainly some amount is likely. I will have to wait until Thanksgiving to get more information on that.

Considerable is created when using the self-clean function of the oven. 

My own oven gives off between 28 and 3 PPM for the first 1-1/2 hours of the 3 hour cycle.  After that time, whatever was creating the CO was successfully incinerated and CO levels dropped to normal. 

These amounts are perhaps not enough to kill you, but certainly enough to affect a person–especially infants that might be around.

In the first 15 minutes of operation, my own oven gave off about 28 PPM, after about half an hour it settled down to 12 PPM and after about an hour it was down to 5 PPM.  At the one-hour mark, ambient CO levels in the kitchen 10 feet away from the oven hovered around 3 PPM—with the exhaust fan on and a window open.

I suspect the amount of CO will depend on what the oven is burning off in the cleaning mode, and levels likely could be considerably higher, and for longer periods of time, if the oven is not cleaned very often.  I clean min probably twice a year.  I may start doing it more often now.

Of course your ordinary CO alarm is “not allowed” to alarm, per its listing, at these low levels, so most of the time you will have no idea why you need a nap.

I think the lesson here is to clean your ovens regularly–don’t wait until you can see the bottom of the oven.  You should also run the kitchen exhaust hood the whole cleaning cycle and keep a window open.

Perhaps I will go take a nap, while I wait for the oven to finish.

Charles Buell, real estate inspections in Seattle

Why do I have SO MUCH condensation on my windows!?

This is a great time of year to talk about indoor moisture.

Because we keep our houses more closed up in the winter (unless you live in an area that needs a lot of air conditioning and you keep the house closed up year round) moisture can build up in the warm indoor air. Warm air can hold moisture until it reaches saturation and then it will start to give up that moisture to the cooler surfaces around the home.

Take for example this metal screw that attaches the front entryway door pull handle to the face of the  door.  The staining and moisture is because there is way too much moisture in air at the interior of the home and it is condensing on the cooler metal.  It is bad enough that water runs down and stains the door.


While a little fogging of windows is normal during incidental “steamy moments” like when you do the dishes (does anyone besides me really do dishes by hand?).  If you have condensation on your windows to the point that it starts to run down the glass–YOU HAVE A MOISTURE PROBLEM!

Your windows certainly should NEVER look like the one in this picture–all that moisture and mold is in the living space–not between the panes of glass.


You don’t really have to wonder if you have a moisture problem when your windows look like this–you do have a moisture problem. The next thing will be figuring out why and then doing something about it.

There can be SO many causes of excess moisture in a home that it will not be the purpose of this post to go into great detail about the many causes. This post instead will be about what you can try before you call in the big guns to figure out what has gone wrong with your home.

In the majority of cases it is not the house that is the problem at all–it is the occupants of the home and the fact they do not know how to properly operate the home. Some people’s lifestyles are more problematic than others. If you diligently do the things I suggest and the problem does not go away–then you will likely have to consider other causes that are more related to problems with the house itself.

1. Open curtains and blinds at least a little bit every day. While it may waste a little energy, you don’t want the air that gets trapped behind the curtains to give up its moisture to the cold glass. Adequate circulation of air will prevent this. Condensation is especially problematic in bedrooms that people tend to keep cooler and tend to keep curtains drawn tighter for longer periods of time. Anyone that has slept in a tent in the cold is aware of how much moisture our bodies give off when we are sleeping.

Keeping the entire interior of the home at close to the same temperature is recommended as rooms left unheated will collect the moisture out of the surrounding room’s warm air like a magnet.  Because it cannot hold the moisture, it will store it on the windows and the cold walls behind all the storage boxes in the room. For example if you have block-out blinds or Venetian type blinds–leave them raised an inch or two to allow for air flow to the glass.

Take a look at these two pictures.  Same room, same humidity and temperature levels.  The first one is the results of condensation with the blinds closed, the second one with the blinds open.



While there is still a little bit of condensation of the glass, consistent with moisture levels being too high, leaving the blinds open prevents a worse build-up of moisture.

2. ALWAYS, run the bathroom exhaust fan for at least an hour after every shower. If you have a way of warming the bathroom into the upper 70’s for a few minutes prior to taking a shower, the warmer air will hold more of the moisture from showering and can then more easily be exhausted during and after showering. If you have condensation running down your mirror or the bathroom window after showering, you are not using your bathroom properly. And another thing–get rid of those dang water saver shower heads that atomize the water making the water easier to disperse into the air. There are other types of water saver shower heads.

3. ALWAYS, use the kitchen range hood while cooking and for a few minutes after cooking. Always use the kitchen fan when the dishwasher is running or even while you are washing dishes by hand.

4. No Grow-ops in the house—legal or otherwise. A few house plants will not cause a problem if all other things in the home, including the inhabitants, are behaving properly.

5. Make sure the laundry exhaust fan is used while doing the laundry. If you don’t have a laundry fan–consider having one added.  Modern construction would require one. Another thing about the laundry is that if the exhaust duct is restricted enough to increase drying time, more dryer moisture will find its way into the home. Making sure that the dryer is behaving properly is important in maintaining proper moisture levels in the home.

6.  Don’t hang laundry to dry indoors.

7. Make sure that all exhaust fans are functional–just because they turn on and make noise does not mean they are doing the job they are there to do. A simple test is to cover the entire grill with tissue and see if the fan uniformly holds the tissue in place. Make sure you do this test with any doors to the room closed. Doors with inadequate clearances for air to move into the room as the air is exhausted may render the fan non-functional. Improving clearances may be necessary. Another test is to put the tissue on the floor near the bottom of the closed door and then turn on the fan–the tissue should be forcefully sucked into the room away from bottom of the door.  Really tight homes may want to think about whether the whole house has adequate means of bringing fresh air into the home when exhaust fans are operated.  All of this can be further complicated by not having direct vent gas appliances.

8. If you are going to cook and bathe in your home it is imperative that you maintain an indoor air temperature above 65 degrees F. I know we all have energy consumption considerations but if you keep the home at 64 degrees (or areas of your home at 50 degrees) and save $200.00 a year in heating costs and cause $2000.00 in water damage you have not accomplished much in terms of saving money. Health costs may also be affected as keeping homes cooler may result in poor indoor air quality conditions.  This cost/benefit ratio is even worse if we are talking about keeping isolated portions of the home cooler. Just heat your home–it will reward you for it.

So, try these things–if you still have nasty looking windows like in the picture above–call a qualified home inspector or indoor environment specialist to figure out what is going on.

By Charles Buell, Real Estate Inspections in Seattle

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What is perhaps the single most important thing you need to know about the modern home you live in?

There was once a time when houses could be neglected in many ways and not suffer the way they will today if neglected.  The opposite started to happen when we started to insulate our homes to save energy.

Inefficient older home

Inefficient older home

The interiors of older homes, for all intents and purpose, communicated very well with the exterior.

They were drafty.

This draftiness allowed for a sort of built-in means of changing the air on a regular basis.  In fact the air changes were more or less continuous.  The key to saving energy was to figure out a way of stopping these air changes.

So we started, insulating, and taping, and insulating, and caulking, and insulating, and vapor sealing–and then insulating some more.  The result was that we started having houses that were very successful at stopping air movement and we no longer had to spend 1/2 the year cutting wood to heat them.

But along with this saving of ax handles, energy and money came an unanticipated cost.

Poor indoor air quality.

Poor indoor air quality manifested itself in the trapping of all sorts of nasty particulates inside the home.  Chemicals out-gassing from interior components and furnishings, dust from pets and human occupants, and the growth of mold due to elevated moisture levels and poor circulation, were just some of the things trapped in the home.  There was also the byproducts of combustion related to fossil fuels and solid fuels burned in the home.  Many other sources of indoor air pollution contributed to this soup of poor indoor air:  air fresheners, incense, candles, detergents, hair spray, paints etc.

So as a result, after figuring out that we could indeed stop air movement almost completely, we figured out that it was a very bad idea and that we better figure out a way to have “controlled” air movement.

In modern homes we provide a way  to mechanically ventilate the home–to provide air changes.

Every time we turn on an exhaust fan, we are removing air from the home and “theoretically” we are pulling fresh air into the home somewhere else.  These fans can, and should, be placed on timers to maintain ventilation according to predetermined times.  Often leakage around doors and windows will suffice as a place for fresh air to be pulled into the home.

Newer more efficient home

Newer more efficient home

Modern doors and windows however, are so well weatherstripped and constructed, that very little air leaks into the home at these points and when we turn the fans on they literally do not pull as much air from the home as they should be and the home experiences negative pressure.  Air can then be pulled into the home through the other exhaust fan locations (the dampers in these fans will still let some air by) or down the b-vent chimneys or the fireplace chimneys.  I think everyone can appreciate that using the furnace b-vent as an air intake is not a good idea.  It will also result in air being pulled under the baseboards or around crawl space hatches, leaving that characteristic “black ghosting” that everyone worries is mold–but is in fact just dirt being filtered by the carpet as air comes and goes from the building.

Because of this we want to provide actual locations where the air can come-and-go from the home whenever the indoor environment is placed under positive or negative pressure.  Sometimes this is done by little vents in the windows or walls or by automatic dampers that are part of an air intake into the forced air heating system.  Most structures deal fairly well with small pressure differentials but when they become great enough, moisture vapor can be pulled or pushed to places we don’t want moisture to be.

With two or three bathroom exhaust fans, the kitchen range hood, the gas furnace/water heater, and the dryer all running at the same time we can create quite a bit of negative pressure and that air that is being exhausted has to come from somewhere–or bad things start to happen.

The vast majority of homes in the United States have inadequate means of balancing the air that is being exhausted.

It is not rocket science as to why so many homes suffer from air quality issues right along with their occupants.

Perhaps the best way of all to manage this air exchange is to install an HRV or Heat Recovery Ventilator.  These are great because as they exhaust air from the home the outgoing air stream passes over the incoming air stream so that the warm air leaving the home can heat up the cold air coming in–and visa versa in Summer.  Of course the air is filtered in the process as well.

In the State of Washington we are lucky enough to have an Energy Code that is very specific about the installation of these air exchange systems.  Even if you live in a state without an energy code (or perhaps especially if you don’t), I consider it prudent to not only ask the following question but to understand its answer:  “When I turn on an exhaust fan in my home, how is fresh air getting in to replace the air that is leaving?”  If you cannot answer that question or did not even know that the question should be asked, you may not adequately understand how to take care of your house and your home may be at risk of poor indoor air quality.

While there are other important things to know, it is the control of the air changes in the home that is perhaps the single most important thing that every owner (or tenant) of a modern home needs to understand–and yet, based on my experience as a home inspector, very few do.

A home inspector with some training in building science (and shouldn’t they all be so trained?) can help you assess how your home is functioning and/or how it should be functioning.

By Charles Buell, Real Estate Inspections in Seattle

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