Relative Humidity, Lungs, Windows and You

Water gets everywhere, sometimes. And it gets into the air, but never exactly the way we want it to. Managing moisture in your home is an important part of being energy-smart, comfortable and healthy.

The glass at left is a window, in a home, in cold weather, condensing water on the inner surface. The glass, to get just a teeny bit technical, has reached a temperature below the "Dew Point" of the air inside, resulting in "dew," or condensation, accumulating on the cold glass.

So? Natural phenomenon, you say. Well known fact, water beads up on mirrors in hot bathrooms, on windows in cold weather, on your spectacles when you come inside on a cold day. Way of the world, Circle of Life, all that. Fair enough. But how much condensation can the windows handle before they rot? How much condensation can take place in your walls (and on them) before mold begins to grow and your air becomes unhealthy? How much moisture should be in the air for your lungs to remain healthy and comfortable all winter?

We'll come back to the specifics in future posts. For now, in this introduction, just realize that your lungs, your walls, your house plants, your pets, your old piano and your light-sleeping partner who hates your snoring all have an interest in how much moisture lives in the air in your house. Don't neglect to use the link above to hear the Lion King theme. I do this stuff for you, you know.

Insolation: Life's Not Fair

Insolation is a word that looks wrong, but look again. Not "insulation," but something entirely different. Insolation is the measure of how much solar radiation falls on a horizontal surface in a location per hour during daylight.

What heats up my sunroom is solar energy filtering through atmosphere, clouds, rain, trees and leaves, bug poop, dirt and glass before entering my house and being absorbed as heat by floor and furniture. In New England we get a certain amount, on the average, quantified in kilowatt hours (like the power through your electric meter) per square meter ( I like feet, but engineers can be so, so... metric) per hour. Insolation varies from sunrise to sunset, changes as clouds and fog drift over the land, and varies seasonally as the sun rises higher and sometimes not as high in the sky.

What frosts my root beer is that we get around 3 of these units of insolation, on average. And Taos, New Mexico gets...... 7. See the map, or use the link to get a larger image. Yes, there's a slight difference of latitude, yes the climate is drier, but it's not fair. If New England got all the solar energy that New Mexico gets, we could...... be New Mexico, I suppose.

The reason our solar panels are only a fraction as productive as those installed in the Sun Belt, the reason our sunrooms don't heat our houses completely, the reason our porches and decks are only fun to use for four months a year or so, is a blend of factors including temperature, cloud density, latitude, rainfall and forestation (frequency, height and shade potential of trees).

And I don't like it. But I'm not moving. So beware when solar panel salespersons, greenhouse companies, window and door manufacturers promise you amazing results from solar heating. We get some, yes, but not as much as Taos, or Miami, or Atlanta. And in March, when I'm tired of being cold, I think we don't get our share.

The Magic of Glass- Now Double It

In my last post we described the progress of a sunny day in my addition. But what makes it work? Why is window glass so nifty as a solar collector? And what technology drives the improvement of windows as selective conductors of light, heat and air?

Simple clear glass is selectively transparent to light and heat. The diagram is not terribly technical, just illustrative. The sun's rays are mostly (except for ultraviolet) passed directly through into the room, and at least some of the infrared (radiant) energy is trapped, making clear glass a pretty good collector of solar heat.

When you double the window with two panes of glass, and add an inert gas in the space between panes, you've decreased light transmission very little (app. 10%) and decreased conductive and radiant heat loss by almost 50%. Well done, Andersen! We're getting warmer as we go.

Add selective coatings (called "low E", mostly) to filter radiant energy going in either one or both directions, and you've affected solar heat gain a little (another 10% or so) and reduced radiant losses by another 30% or so. This link may help.

It's hard to refine the glass window as a filter much beyond that, although the engineers, God bless them, will never stop trying (as long as we pay them, and even then, they have garages). As you increase the filtering of radiant energy through the glass, direct light transmission also suffers, and you get eventually to a window that puts one in mind of Paul's phrase "seeing through a glass, darkly." See our previous post on "super windows."

The strategy of using window coverings as nighttime filters for radiant and conductive energy through windows is difficult to escape. I've seen automatic pully arrangements with insulating covers, and the Somfy company gets very geeky with light sensors on motor-driven shades, but if you're an energy player, so to speak, you won't mind operating your shades/drapes/panels at sundown and sunup, turning windows into walls when they aren't working for you as solar collectors. We'll try to get back in the next few days, as work permits, to continue this discussion of windows and sunlight.

Passive Solar- Not Sexy, Just Smart

South facing windows don't always give you the view of this photo, but any view that includes the sun for most of the day is an energy-rewarding one. There is much to know about the unfairly labeled "passive solar" approach to architecture, and I'd like to spend a few posts exploring the basics together.

Let's start with a bright morning in my addition (the photo is not mine, nor is that scrumptious view). The sun rises, depending upon the season, somewhat southeast at my latitude, 41.4 degrees north. As the sun clears the tree line, app. 500 yards from the house, four ordinary thermopane windows in the south wall start to pick up the sun. Roman shades are raised early in the morning, exposing the glass. By mid-morning, two skylights in the 45 degree sloped roof begin to cast bright, hot rectangles on the wall and floor. By now the room, underserved by my warm air heating system, is already the warmest in the house.

At noon the sun is at its highest point, and is passing the corner of the addition, which is aimed 15 degrees northeast. The house dates from about the Civil War. I didn't choose the site orientation. A four foot square casement window starts to pick up the sun and spread light across the dark harwood floor. Around two p.m. a six foot sliding glass door is filling the room with near-blinding light and more heat. It's ok, really. No one's home at that time, and I refuse to draw the curtains and lose the heat. Thou shalt not muzzle the ox, and all that Biblical wisdom.

By five p.m. it's all over. The sun reaches an artificial horizon to the southwest, a tree-lined hill that crests a quarter-mile away. And then it gets dark, we come home gratefully to a warm room, the ceiling fan has wafted lots of heat through a huge pass-through door to the rest of the house, and we drop the insulating shades and use the thermostat, if necessary, to finish heating the house for the evening. We'll be back next time to go over this scene in more detail.

Just Stand There While I Plug This In

There is a persistent urban myth about the invention of the GFCI involving skeptical investors and industry officials, a bathtub, a toaster, the inventor's beloved only daughter and a Ground Fault prototype, but it never happened. There is some truth to the idea that the early "Residual Current Protective Device" encountered some resistance from a conservative building industry following its invention in 1961 by Charles Dalziel, an engineering professor at UC Berkeley. Similarly persistent rumors about his use of graduate students to test human shock tolerance, sadly, are confirmed.

Gradually since the early 70's the GFCI has conquered the building trades until by now its use is required in new houses and remodeling projects to protect bathrooms, kitchens, garages, basements, swimming pools, outdoor receptacles and hot tubs. If you don't see these rather official-looking plugs with buttons on around your house, it probably means you haven't had your wiring updated by a professional for many years.

I get shocked about half a dozen times a year; usually I deserve it. I'm a professional electrician, among other things, and the risks I take are deliberate and, hopefully, warranted. Once in a while I simply stumble upon a live wire left by some amateur or careless professional. Then I get all high and mighty and throw things and shout, "Somebody oughta do something about these nitwits!" I've acquired the habit of wearing basic gloves when in "terror incognita" wiring situations full of unknowns and hidden dangers.

If you have at least one GFCI or a prime suspect in the house, and a group of other receptacles suddenly and mysteriously goes silent, you must suspect that they are connected downstream of the device, a cost-cutting measure sanctioned by the Code but avoided by curmudgeons like me who hate charging to show up and push a button. Reset your GFCI, and the dining room plugs will probably wake up and smile.

Last tip: go to the home center and buy a plug tester, pictured at the head of the post. Following the simple instructions you can test any three prong outlet for a number of conditions, and test GFCIs for proper function, without taking any risk at all. Then you can say to me, on the phone, "The tester says 'open neutral,' and I heard a humming from inside the box. I found the breaker and turned it off. Can you get here tomorrow?" That never fails to impress.

It's a Short! It's a Surge! No, It's a Ground Fault

If you've never dropped a power tool into a puddle or cut (yes, I'm thinking of you, dear daughter) a live wire with pliers, you don't know how hard your fuses or breakers are working for you down there in the panel. Your house has not burned down, like too many others, because the practical and safe limits of your wiring are being enforced by protective devices.

Unless your house is a true antique, you probably have GFCI plugs in it somewhere. Funny rectangular duplex receptacles with buttons on the front that protect you from different threats than those dealt with by breakers. GFCI receptacles are wonderful devices that trip in the presence of "ground faults."

Don't worry about ground faults that take place inside boxes or in your panel. they usually don't hurt people, they just make work for guys like me. The ground faults you need to be protected from are the ones you create. You splash water on the counter while filling the coffee maker. You wash out the bread machine and don't let it dry enough. You reach for that old radio just after getting out of the shower. You wash the car, then set the vacuum on wet pavement to clean the inside. Here's a Youtube link to the classic James Bond scene with the radio in the bathtub. Shocking.

The Electrical code now requires new houses to feature GFCI receptacles in kitchen, baths, basement, garage and on porches. Here's a link to show how you test and reset them. We'll do another post on GFCIs and tell a bit of their history and workings.

More Watts To You

In the last post we gave you Rule One, label your circuits, and Rule Two, read the labels on your appliances and calculate your loads, limiting them to 1500 watts for safety and to avoid tripped breakers. In fact, kitchen circuits can handle a bit more (1800 watts, if they're wired correctly for 20 amps), but it's best to stay in the safe zone.

Rule Three is: be familiar with your "occasional" loads, and be wise about using them. Occasional loads are things you use only when you decide to: blow dryers, vacuum cleaners, bathroom space heaters, fax/copy machines and power tools all qualify. And before you plug in that saw or heater, think---- what circuit is this, and what else is on right now? If you've never heard a breaker moan when it picks up a big load (I am NOT making this up), believe me, they feel it when they operate near max capacity.

Rule Four is: Throw blown fuses away. Throw them away! I go into too many basements and find a row of dead ones lining a shelf or sill, "waiting to be healed," as Garrison Keillor says. If you want a reminder to get more, put one into your pocket or purse. You won't be down there again until you blow another fuse. You need to take note of three things about a fuse: amperage (15, 20, 25, 30), base thread size (the part that screws into the panel; there are two sizes, large and small), and response time (time delay, simple fast-blow; the home store staff can help you with this).

Rule Five, and last, is: Learn to reset a breaker. The little handle falls back either to the opposite position when it trips (most breakers point to the centerline of the panel when they're on, a few [Federal Pacific, Westinghouse] point outward), or sits in the middle. Learn this before you're in trouble. Push the handle all the way into the "off" position, wait a second in case it's still hot from tripping, then push back toward the "on" position. Gently. Don't use a tool of any kind. Better to break a ten dollar nail than to snap a breaker handle or get a tool involved in the live parts inside. Easy does it, as the AA saying goes. If the breaker won't move to firm finger pressure, come back in a minute. If it's still stuck, it's been damaged and you'll need a licensed person to replace it. Here's a link to a good how-to site.

If anything about this process scares you, don't touch the panel. If anything looks broken, if the cover falls off, if you smell anything funny, if you feel any heat coming off it, back out and pick up the phone. Don't get hurt proving you're tough and self-reliant. There are panels I won't touch, and I'm the pro. Until next time, keep a good flashlight handy, and send along your questions before wading in.