Replacement Windows: No Big Secrets, Some Negative Aspects? (Part 1)

by Scott Best - Date: 2007-03-26 - Word Count: 1243 Share This!

It's true that replacement windows save money in energy costs. It's true that the proper replacement windows, installed properly can add value to your home. It's true that the cost to replace windows today is by comparison, cheaper then it has ever been. These are all truths about window replacement that have a provable factual basis. What is also true is that 70% of homes 10 years old or more can benefit from the installation of replacement windows. Of course, the older the home the greater the benefit will likely be, words of wisdom that you've probably heard before as well.

Over time window sealing effectiveness deteriorates and energy is lost through the leaks around windows. Of course that information isn't new either. So to save energy or add value, home owners often replace windows and doors without considering some of the negative aspects of having a tightly sealed home.

Actually negative might be the wrong word to use. I hesitate at using the word negative, because it might sound as if I were advocating against replacement windows, which is not the case at all. Rather I think it is important to be aware of changes that replacing windows might bring about in the home. Two things come to mind that may need to be addressed along with windows and door replacement. These things can cause some potentially serious problems.

The first that comes to mind is the changes in indoor air pressure. If you have electric heat or a newer (within the last 5 years or so) thermo efficient gas or propane heating system, air pressure may not be a concern. Still you may want to think about the information presented and apply it to investigating your own home situation.

Why would we be concerned about air pressure in the home? Many homes over the last ten to twenty years, in many parts of the country have opted for such things as under floor and baseboard hot water heating, systems that utilize a boiler to heat water and circulate it throughout the home for heating purposes. When these systems were originally being installed, little thought was given to where the oxygen would be coming from that would complete the combustion process that the boilers need to heat the water.

Why would we need to think about such things? Well twenty years ago we probably didn't need to. But with homes being build tighter and tighter all the time, it has become more of a concern, here's why.

A gas or propane heating system, regardless of how it operates, either by circulating hot water from a boiler or via an induction type forced air system; they all require air, or oxygen to complete the combustion process to create heat. So where does this oxygen come from. Well for the most part it comes from the air that we utilize inside our homes. In older homes, where there were always tiny leaks in different places throughout the home made it possible for these heating systems to draw in enough air to operate smoothly. People never really noticed any problems and paid the cost of fuel. Already you might be seeing the fallacy in thinking everything was well.

• Air comes in through tiny cracks around windows and doors

• Heating system burns air from within the home to heat the home, causing more air to be drawn in through tiny cracks around windows and doors (cold air)

• Temperature falls because of the influx of outside air around leaky windows and doors

• Heating system burns air from within the home to heat the home, causing more air to be drawn in through tiny cracks around windows and doors (cold air)

• Temperature falls because of the influx of outside air around leaky windows and doors

You get the idea, and all this time homes were hemorrhaging money via fuel consumption. No one thought about it too much until the cost of fuel and energy started to climb rapidly. So people begin to attack the problem but where to start. Usually two areas of thought prevail, and those are more insulation, and stopping up the cold air flow around windows and door. It's what we were told to do right? Absolutely.

So now we seal up the windows and doors either by replacement or maintenance, add more insulation and the result is a nice warm tightly sealed home that is more energy efficient right?

Yes and possibly no. Here is the catch for older homes with out dated heating systems. Creating a tightly sealed home can actually cause your older heating system to work harder and use more energy. How is that possible? By sealing up all those places where the heating system was drawing oxygen for combustion, we have effectively starved that combustion almost to death. Sometimes that sealing off of incoming air it so effective as to make that system quite ineffective as a heating source and creates negative air pressure in the home.

How can you know if you have a negative air pressure situation? Just open a door. If you hear air suck past a door when opened while the heating system is engaged, then you can be almost certain that a negative air pressure situation exists. If a negative air pressure situation exist, then you can be assured that your heating system isn't running as efficiently as it should. It isn't getting enough oxygen to complete the combustion process properly, thus wasting fuel. Another big clue that you have a negative air pressure situation is that you find a point or two that you now notice very cold air coming from in the home that you never noticed before. Not that the spot is by comparison cooler then others in the home, places where you can actually feel the cold air rushing in.

The reason that these cold spots develop in a negative air pressure situation, after windows and doors are replace is because your heating system that in the past had multiple places to draw air from, now only has a very few, and to maintain the combustion process, it must draw a greater volume of air from the few remaining sources making them more noticeable.

So we fix one problem and end up with another. But the solution is rather simple. Just replace the heating system. Simple right? Ok, so that isn't funny, but there is a lesson to be learned, which new heating systems have taken into account.

New heating systems generally take into account that homes are more tightly sealed then ever before, and in knowing this they have provided the heating system with its own outside air source. Usually a two or three inch PVC pipe through an outside wall, one that is as close as possible to the unit's location. In doing so, the need to draw air through the rest of the house is effectively eliminated, while supplying all the oxygen needed for healthy and energy efficient combustion at the heating unit.

The reason that the outside air source needs to be as close as possible has to do with the path of least resistance law of flow. Air just like water will take the path of least resistance when flowing. If the provided outside air source is too far away, and the system can draw oxygen from a closer source easier, it will do so.

In part two of this article I will discus another major concern that may need to be dealt with when replacing the windows in your home.

Related Tags: replacement windows, vinyl windows, casement windows, pella windows, anderson windows, double hung

Scott Best is a freelance writer in association with Read more of his articles at Your Article Search Directory : Find in Articles

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