QUESTION: It gets chilly and drafty near our aluminum sliding glass patio door and I feel a warm air leak in the summer. What type of replacement doors are best to block both the cold and heat and lower our heating bills?
ANSWER: A typical metal sliding-glass patio door is one of the most energy-wasting items in a house. To exacerbate the problem in the winter, you feel chilly from the drafts, so you set the room temperature higher to compensate.
The three most important factors to consider are the basic design (sliding or swinging), the frame material and the type of glass. The basic design and frame material have the greatest impact on the airtightness of the door. The type of glass impacts the conductive heat loss the most.
Double swinging (French) doors can be designed to seal very well. With swinging doors, much of the weatherstripping can be the compression type. If you chose insulated metal doors, super-airtight magnetic seals, like on your refrigerator door, are used. Compare the air leakage (infiltration) specifications for each door you consider.
However, before you consider swinging doors, make sure you have adequate open area in your room for the doors to open. Sliding doors are real floor space savers because you can place furniture near them.
With any type of sliding-glass door, a very strong frame material and good design are important. These doors take a lot of impact abuse. They must remain true, otherwise even the best weatherstripping won't be effective.
There is a new type of sliding-glass door with a unique track design. The door closes in a similar fashion to an airplane door. They are flush when closed. This provides one of the most airtight seals. It is also very secure against break-ins.
The frame is made of special fiberglass. Fiberglass is very strong and it expands or contracts very little with temperature and humidity changes throughout the year. Unlike vinyl and aluminum, you can easily paint the fiberglass frame to change colors if you desire.
The glass options for patio doors are the same as for windows. The two most energy-efficient glass systems are Heat Mirror and low-emissivity (Low-E) filled with argon gas. Both have an insulating R-value more than three times greater than single-pane glass and they block outdoor noise.
You can write to me for Utility Bills Update No. 370, showing a list of patio door manufacturers (sliding and swinging), frame materials and types of glass they offer, and information on the new fiberglass airplane-type door. Please include $1 and a self-addressed business-sized envelope. Send your requests to James Dulley, c/o Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.
Furnace Cycles but Doesn't Produce Heat
Q: My furnace cycles on and off every couple of minutes, but it doesn't produce heat. What could cause this and what can I do to fix it?
A: The most probable cause is that your furnace is cycling on the fan/limit switch. It shuts off the burners when the temperature inside the furnace gets too high. This is often the result of inadequate air flow through your heating system.
Check to make sure the furnace filter is clean and not blocking the air flow. Check the tension adjustment on the blower belt so it isn't slipping. Make sure the duct dampers are in the open position and that the return registers aren't blocked by carpets. If everything checks out properly, you should contact your service technician.
Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.