Re: Article about Old Houses vs. New Houses

[Guest guest]

Here's the entire article.

About the House: The Fight Between Old Houses and New Houses

By Matt Cantor

If you stop and think about it, the notion that old houses are better

is just as silly as the notion that new houses are better. The truth

is that both things are true. Older houses are better in some way and

newer houses are better in others. Construction is fraught with

misconceptions. Another one is that the framing or " bones " of old

houses is better than that of newer ones.

While it's certainly true that our older housing stock has, within

its walls, some of the best timber ever permitted cut dried for these

purposes, the manner in which they are conjoined is inferior to

current methods and come the next earthquake, I'd rather be in a

house that had been built last year than one built in 1920. Of

course, one can take the older house and add the hardware that the

newer house has and also withstand the big one when it arrives (which

is my idea of the perfect house).

In recent years, the housing industry has gotten itself in some deep

you-know-what as a result of one of its greatest successes, the

perfection of the tight house. Houses in the last 20 years have been

pushed to such low porosities (the rate at which moisture or gases

pass through them) that they lose nary a Therm (a unit of heat

measurement). While the goal of making houses energy efficient is a

brave and worthy one, the consequences of living in these wooden

vacuum bottles are growing more apparent every day. Too many of them

are rotting away and sometimes in a matter of months. O.K., I'm being

a bit hyperbolic but it IS true that massive fungal infestations are

being found in many of this new class of house all across the country

but particularly in those areas where humidities run high.

Understanding how ventilation works and how moisture moves with air

is becoming an important aspect of architecture, building inspection

and construction as we all try to respond to this nasty bit of news.

So, why is this happening and what changed. In short, older houses

evaded these moisture related problems by leaking. They leaked air,

they leaked moisture, they leaked heat. Apparently, this was not so

much of a problem as we had formerly thought! Leaking, it turns out,

is a good thing, but as with our initial premise, it's also bad. It

depends on what you're testing for and what you want.

If you want a house that has a good " drying potential " (the ability

to dry out quickly after leaks occur) you get a big thumbs-up. If you

want a house that's going to hold onto a given amount of heat for any

length of time, it's thumbs down.

A large number of mold-related cases in the recent past have involved

newer, tighter houses. Like huge colonies of Stachybotrys chartarum

(the favorite of the legal community), these cases having been

growing exponentially and are flooding the courts in increasing

numbers and all because people, including those in the construction

community, fail to understand some basic (and not-so-basic) things

about how buildings work.

If you create a tightly sealed environment, one that does not dry out

quickly, and you allow a little water to leak into it through a

shoddily built wall, you can end up with water sitting for an

extended time inside something not all that different from a

cardboard box. Get the picture.

Actually, this whole problem is even worse with newer houses because

the wood products used in most newer homes are so much more

digestible than those in older homes that the rate at which they get

consumed by fungi can be impressive.

So all around, it's a bad scene and if you own a relatively new house

the word is simple, keep the water out, period. If you see any sign

of leakage, have it fixed properly and quickly.

Now, let's get back to our older home. If an older house, with its

high porosity, leaks at a window, a roof or right though a wall, the

water hangs around for a much shorter period and the likelihood of a

mold or other fungal problem (molds ARE funguses) is greatly reduced.

Older homes and most newer ones as well, were, and are, designed to

allow air to pass under them as well as through attic spaces. This

does a range of good things for us but none so good as the removal of

damp air and replacement with dryer air. In places where Radon is of

concern (and this is generally low in our area), the exchange of air

also helps to remove this potent carcinogen (second only to

cigarettes in lung cancer deaths at around 20,000 per year).

If it's wet under your house, some of that water is going to

evaporate and find it's way into the structure. In houses where

crawlspace ventilation is poor, there is consistently more fungal

growth (molds included). In houses where enough ventilation is

provided, the presence of destructive fungi is much lower and usually

the result of a leak from plumbing or from rain entry.

Ventilation is also something that's easy and cheap to provide.

Crawlspace vents are really nothing more than a series of holes

though the sides of the house below floor level that allow air to

flow through the crawlspace.

These vents require screening for the sole reason that critters of

various sizes and nastinesses favor the space below your house for

their dinner parties ( " another grub, Madam? " ), romantic liaisons

( " You smell like rat, my darling. Come to me now " ) and infant

deliveries ( " Look honey, Octuplets! " ). The ideal screening is heavily

galvanized steel mesh. This is available a range of pre-cut and

framed shapes that can be installed quite easily. If you're adding

ventilation because you are aware of the moisture in the crawlspace,

I would also recommend adding a plastic barrier laid directly upon

the soil. This helps control moisture and requires no sophisticated

installation.

Ventilation requirements in new construction vary but are generally

around 1 square foot for every 150 square feet of crawlspace. This

means that most houses I see required around eight square feet or

around 16 vents distributed around the house (they're typically a

square foot each). Vents do the most good when the wind can get to

them so vents that are close to fence or blocked by bushes should be

considered to have less value. If you're adding them, try to place

them where they're more likely to create cross-ventilation.

It's worth noting that very few houses meet this requirement and many

would clearly benefit from their introduction. Recent codes have

allowed a radical reduction in the ventilation requirement for houses

(one square foot per 1500 square feet) when vapor barriers are

properly installed and where the vents are placed near the corners

for improved draft.

My personal take is that this is short-sighted and that when moisture

is present, all the big guns should be brought out and used. If a

house is essentially dry underneath, I'm fine to see this radical

reduction in ventilation but in crawlspaces where we know it's been

getting wet, adding loads of ventilation as well as vapor barriers is

cheap and sensible and there's really no good reason to avoid it,

unless, of course, you happen to like things wet and slimy, but hey,

knock your amphibian-like self out.

--- In , " charlesb35 " <charlesb35@...>

wrote:

>

> This is an excellent article about old houses vs. new houses and

the

> effect of moisture problems on houses that are built too tight.

>

> Be sure to read the entire article at:

>

> http://www.berkeleydaily.org/text/article.cfm?issue=09-21-

> 07 & storyID=28064

>