Draw a line across the country at the latitude of lower Pennsylvania.
Any house built now below that line without air conditioning will be obsolete in 10 years.
Fortunately, it is the FHA which has arrived at this conclusion, for it means that cooling equipment of all kinds may now be included in a mortgage, and thus acquired with a minimum of financial stress.
Even if you live above that line, the FHA will back you, for they have decided that the inclusion of air conditioning in all new homes is a good thing and should be encouraged.

New simplified packaged units, recently devised prefabricated glass-fiber ducts, and improved add-on techniques make it possible to acquire a system for an 1800-square-foot house for as little as $600 to $900.
Two men can often do the installation in a day.
You can install it yourself -- this is a central system that will cool every part of your house.
Its upkeep?
No less an authority than the FHA concurs that the savings air conditioning makes possible more than offset its operating costs.
Is it worth-while?

Home air conditioning has come a long way from the early days of overcooled theaters and the thermal shock they inflicted.
We know now that a 15-degree differential in temperature is the maximum usually desirable, and accurate controls assure the comfort we want.

We know, too, that health is never harmed by summer cooling.
On the contrary, there are fewer colds and smaller doctor bills.
The filtered air benefits allergies, asthma, sinus, hay fever.
Control of temperature and humidity is a godsend to the aged and the invalid.
Heart conditions and high blood pressure escape the stresses brought on by oppressive heat.

Housekeeping is easier.
The cleaner air means less time spent pushing a vacuum, fewer trips to the dry cleaners, lighter loads for the washing machine.
The need for reupholstering, redecorating, repainting becomes more infrequent.
Clothes hold their shape better, and mildew and rust become almost forgotten words.

It will improve your disposition.
When you're less fatigued, things just naturally look brighter.
The children can have their daytime naps and hot meals, and be put to bed on schedule in shade-darkened rooms.
You'll sleep longer and better, too, awake refreshed and free of hot weather nerves.

You can forget about screens, and leave the storm windows up all year around.

Best of all, central air conditioning is something you can afford.
Like its long-lived cousin, the refrigerator, a conditioner can be expected to last 20 to 25 years or more.
That brings its per-year cost down mighty low.
For any house.

No matter what style your home is, ranch, two-story, Colonial or contemporary, central air conditioning is easily installed.
The equipment won't take up valuable space either.
It can go in out-of-the-way waste space.

But there's no denying that the easiest and most economical way to get year-'round whole-house air conditioning is when you build.
If that's done, the house can be designed and oriented for best operation, and this can mean savings both in the size of equipment and in the cost of the house itself.

If you can't see your way clear to have summer cooling included when building, by all means make provision for its easy adding later.
Manufacturers have designed equipment for just such circumstances, and your savings over starting from scratch will be substantial.

If your house is to have a forced warm air system, cooling can be a part of it.
This costs less than having a completely separate cooling system, for your regular heating ductwork, filters and furnace blower do double duty for cooling.
You can get year-'round air conditioners in the same variety of styles in which you buy a furnace alone -- high or low boy, horizontal or counterflow.
The units can be installed in basement, attic, crawlspace, or in a closet located in the living area.
The cooling coil is located in the furnace's outlet.
From the coil small copper pipes connect to a weatherproof refrigeration section set in the yard, garage, carport, or basement.

If you plan to add cooling later to your heating system, there are things to watch for.
Be sure ducts that require insulation get it when they are installed.
They may be inaccessible later.
Be sure your ducts and blower are big enough to handle cooling.
This is especially important if you live in a mild-winter zone.
Be sure you get a perimeter heating system, and diffusers that will work as well for cooling as they do for heating.

You can get a hot water system that will also work for cooling your house.
For cooling, chilled water is circulated instead of hot water.
Instead of radiators you'll have cooling-heating units, each with its own thermostat.
These systems are more expensive than year-'round forced air systems.
The minimum cost for an average one-story, 7-room house with basement, is likely to run $1500 above the cost of the heating alone.
Separate systems.

If the problems of combining cooling with your heating are knotty, it may be cheaper to plan on a completely separate cooling system.
The simplest kind of separate system uses a single, self-contained unit.
It is, in effect, an oversize room conditioner equipped with prefab glass-fiber ducts to distribute the cooled, cleaned, dehumidified air where it is wanted.

In a long, rambling ranch, two such units can be installed, one serving the living area, the other the sleeping zone.
In a two-story house, one unit may be installed in the basement to serve the first floor, another in the attic to cool the second.
In each case, having separate systems for living and sleeping areas has the advantage of permitting individual zone control.
The heat pump.

One of the more remarkable of the new cooling systems is one that can be switched to heating.
As you know, a conditioner makes indoor air cool by pumping the heat out of it and then releasing this heat outdoors.
A relatively simple switching arrangement reverses the cycle so that the machine literally runs backward, and the heat is extracted from outdoor air and turned indoors.

Up until recently, this heat pump method of warming air was efficient only in areas of mild winters and when outside temperatures were above 40 degrees.
Now, the machine has been improved to a point where it is generally more economical than oil heat at temperatures down to 15 degrees.
You can get this added heating feature for as little as $200 more than the price of cooling alone.

Consider it as a standby setup, at negligible cost, for those emergencies when the furnace quits, a blizzard holds up fuel delivery, or for cool summer mornings or evenings when you don't want to start up your whole heating plant.
What size conditioner?

How large a cooling unit you need, and the method of its installation, depends on a variety of factors.
Among other things, besides the nature of your house and how much heat finds its way into its various rooms from the outside, it will depend upon your personal habits and the makeup of your family.
Families with children usually don't want the house quite so cool.
If you are a party thrower, you may need added capacity.
The body is a heat machine, and 20 to 25 guests can easily double your cooling load.

Cooling requirements are best expressed in terms of Aj.
A BTU is a unit of heat, and the BTU rating of a conditioner refers to how much heat your machine can pump out of your house in an hour.
A very rough rule of thumb is that, under favorable conditions, you'll need 15 BTU's of cooling for every square foot of your house.
This is if outdoor temperatures have a high average of 95 degrees.
You'll need more if the high average is above that, less if it's below.

Coolers are also rated by tons.
A ton of cooling compares to the cooling you get by melting a ton of ice.
By accepted definition, a 1-ton conditioner will provide 12,000 BTU of cooling in one hour.

You may find a conditioner rated by horsepower.
It is generally an inaccurate method of rating, for the horsepower is that of the compressor motor, and many other components beside it determine how much cooling you'll get.
A 1-hp conditioner, for example, may vary in effectiveness from under 8,000 BTU to well over 10,000 Aj.

The safest procedure is to let your builder estimate the size of the unit you need, rather than trying to do this yourself.

Don't urge your builder to give you a little extra cooling capacity just to be sure you have enough.
Better to have your equipment slightly undersized than too big.
Here's why:

Reducing humidity is often as important as cooling.
An oversize unit will cool off your house quickly, then shut down for a long period.
Before it cycles on again, humidity can build up and make you uncomfortable even though the temperature is still low.
With a unit of the right size, a compressor will run continuously during hot weather, reducing humidity as evenly as it does temperature.
Money-saving tips.

Attention to details can cut in half the size unit you need and pare operating expense proportionately.
A well-designed, 1200-square-foot house can be comfortably cooled and heated for as little as $128 a year, or $11 a month.

If you have a house which heat doesn't penetrate easily, your unit will have less heat to remove.
Keep the direct sun from reaching the house and you've won the first battle.
In a new house, generous roof overhangs are a logical and effective solution.
If the house you plan to buy or build won't have big overhangs, you can still do a fair job of keeping the sun off walls and windows with properly designed trellises, fences and awnings.

Shade trees, too, are a big help, so keep them if you can.
Drawn blinds and draperies do some good, but not nearly as much as shading devices on the outside of the house.

The more directly the sun strikes walls and roof, the greater its heat impact.
The way a house is set on its lot can therefore influence how much cooling you're going to need.
A shift in the walls, or a change in the roof slope, so the sun hits them more obliquely, can save you money.

You can use heat-absorbing glass to stop the sun, double glass and insulated glass to combat condensation.
Restrict large glass areas to the north and south sides of the house.
They're easier to shade there.
An attic space above insulation makes a house easier to cool.
You'll even gain by putting your water heater outside the conditioned space, and using an electric range instead of a gas one.
Gas adds to the moisture load.

Insulate, weatherstrip, double-glaze to the maximum.
In insulation, the numbers to remember are 6-4-2.
They stand for 6 inches of mineral wool insulation in the ceiling, 4 inches in the side walls, 2 inches in the floors.
Such extra-thick insulation not only permits a much smaller cooling installation, but will continue to reduce operating expenses both in heating and cooling.
A light-colored roof will reduce sun heat by 50 per cent.

It costs two to three times as much to remove a BTU in summer as it does to add one in winter, so every solitary BTU is worth attention.
You'll foil them in droves, along with their pal humidity, by having and using a kitchen range exhaust fan, a bathroom ventilator for when you shower, and an outside vent for the clothes drier.
Keeping conditioners quiet.

It's no use pretending that all conditioners are quiet, but the noise they produce can be kept to a minimum.
Good workmanship is important in the installation, so if you're doing your own contracting, don't award the job on the basis of price alone.

Avoid attic placement directly above a bedroom.