Should I replace sliding patio door?

wanttolearn

Hi-

I am not sure if this question belongs on this forum, but I will give it a try:

I have a major problem heating my living room den.  During the winter months, the hot water baseboard is running at almost 100% of the time, and the baseboard gets nice and hot, so it is obviously working fine. 

But the room struggles to get to a comfortable heat of 71 degrees.  On cold days, despite the baseboard blasting heat, the room only get to 68/69 degrees.

I have the walls and ceiling insulated with blow in insulation, and this helped somewhat but did not eliminate the problem.

I now suspect that the problem may be the big patio sliding door in the room.  The patio door is NOT obviously drafty (at least not to the touch...) and just to make sure, I have also applied some weather-stipping to the base and the sides of the door. 

But when I recently took a temperature measurement using an infrared gun, the glass surface of the patio door measured 50 degrees, when the adjacent walls were at 70 degrees.  Is this a normal differential or does it indicate that the patio door is insufficiently insulated?  Could it be that all the heat being generated by the baseboard is just escaping through the patio sliding door?

Will I get a significant improvement if I replace the patio door with a new door with argon gas insulation, etc.?  It is not cheap to do so, so I am reluctant to spend the money without getting some independent advice. 

Any help would be appreciated!

Charlie from wmass

I would figure

what the heat loss is for the room. Then see if there is enough baseboard for the room. Yes glass is colder than walls. You may need to add heat emitter to the zone. be it more base board or a radiator. It sounds like the design temp was warmer than you are actually experiencing, or baseboard was cut short as there was not enough wall for the base line baseboard. Baseboard comes in different ratings. some as high as 1,000 btus a foot on the commercial end.

icesailor

drafty doors:

A third world way to check if the door replacement would help is to take a big blanket and hand it up in front of the door. If the temperature starts going up, there's your answer.  A nice set of heavy drapes that you could pull across the door at night or when it gets really cold. If the sun shines through the door during the day, open the drapes.

Do you have recessed ceiling lights in the ceiling? If you do, shoot your infra-red thermometer in the cans and see what the temperature is. If they are low, you have a heat loss. Take a lit cigarette and hold it up to the light. If the smoke gets sucked in, you have a vacuum cleaner running outside that is sucking the heat out of the room.

Did you shoot the ceiling? What's the temp? You can figure out a lot with a heat gun.

Brad White

I agree with Charlie and Icesailor

good advice to calculate a heat loss and try the quilt trick, plus smoke testing. All good.



As for the surface temperature of glass and wall, yes, what you measured is normal and average for double-pane glass. Of course the outside air and outside surface temperatures are key at that exact time.



Right now where I am, it is about +2 outside. The attached photos I just took in my office show the glass surface (original windows with storm windows outside),  right about 50F and the wall temperature nearly at room temperature where it is insulated, less so in spots. (We are working on it!) But it does show that the surfaces are fairly consistent with yours.



I threw the photo of Silky just for fun.



Edit- I would be reluctant to advise you to change out your working glass window for one of higher energy efficiency just for energy savings alone. Also, the quilt trick or any window quilt for that matter, will not, unless perfectly air-sealed, save you energy. They work by blocking your body's radiant heat loss to the colder exterior glass. Basically raises the mean radiant temperature of the exterior boundary.  I have argued that window quilt systems actually increase heat loss by amplifying reverse convection over the top, down the window and out the bottom. They increase comfort in the moment, but not save energy except to the extent they increase your comfort and forestall you from turning up the thermostat.

Keith M

Do you have a rug in the room?

Most of the heat delivered from hot water baseboard is convective heat. Baseboard requires airflow and it is common for carpet installers to block the air opening at the bottom of the baseboard. The result can easily be insufficient heat.

Attached is a brochure for Fine/Line 30 baseboard. On the top of the last page is a side view of the baseboard. The bottom opening is 1 13/16 inches and that full opening is required to get the full output of the baseboard. The more the opening is blocked, the less the heat output will be. This air inlet opening size varies with different brands and models of baseboard, however all hot water baseboard do have this air inlet opening.

Also, if you have a rug make sure it does not curl up in the bottom of the baseboard and cover the bottom of the element. If it does, it will block airflow and decrease output.

The baseboard will still get hot if the air flow is blocked and it will still deliver some heat. If the airflow is partially or completely blocked, open it up and see if that takes care of your problem. Naturally the damper at the top of the baseboard should be open as well.

Keith Muhlmeister, Slant/Fin Corporation

icesailor

Apples in the door:

Brad,

If you are comparing apples and oranges, you have points. I'm comparing apples. Mac's and Delicious

Storm windows on single pane windows cut heat loss by 1/2. If it is 70' inside and 0' outside, the temperature in the middle of the air space is 35' If you add another pane of glass like double paned glass, the number drops. If it is colder between the drape and the inside of the door, it gives more resistance to the heat flowing to the cold. How much is subjective. But the resistance is there and it works. If you have a drafty, infiltrating door, seal the door. If the door is radiating, cover the door. Especially if it is aluminum. But you don't see too many of those any more.

JMO,

icesailor

Apples in the door:

Brad,

If you are comparing apples and oranges, you have points. I'm comparing apples. Mac's and Delicious

Storm windows on single pane windows cut heat loss by 1/2. If it is 70' inside and 0' outside, the temperature in the middle of the air space is 35' If you add another pane of glass like double paned glass, the number drops. If it is colder between the drape and the inside of the door, it gives more resistance to the heat flowing to the cold. How much is subjective. But the resistance is there and it works. If you have a drafty, infiltrating door, seal the door. If the door is radiating, cover the door. Especially if it is aluminum. But you don't see too many of those any more.

JMO,

Mark Eatherton

Nicely said Brad....

I think MRT is the most misunderstood principle in providing and maintaining good human comfort. Our bodies know more about MRT than we do. Our bodies LIKE it when the MRT is elevated, and the air temperature is lower.



Our electric window can be adjusted to a glass surface temperature matching or exceeding the local MRT, and interestingly, our field research is indicating that it can do so with little to no additional energy being consumed. Not quite what we were REALLY hoping for based on previous studies (KSU), but better than sharp sticks to the eye for sure.



So, essentially, we can make the window disappear as it pertains to conductive heat loss and human discomfort. I have said from the day I was introduced to this product, that is a THE biggest weapon in our bag of tools on the war against human discomfort, and that is what we are confirming in our tests.



I am in the process of programming a PC based programmable logic controller to control the windows up in Hydronicahh to use one 120 volt circuit (20 amp, 2400 watts) to send small darts of energy out to the windows to maintain thermal opacity (glass surfaces around 72 degrees F) using Solid State Relays. The device can switch as fast as once every 1/2 second, and will operate virtually silently.



It will have numerous "modes" and various "scenes". If I program it for a heat production mode, the glass will be allowed to get as warm as 90 degrees F. This will be the typical BOOST mode, and will only be used when pulling the home out of a deep set back hole (going from unoccupied to occupied mode). Once the home is warmed up to set point, and the MRT charged up via the radiant walls, and ceilings, the glass will be maintained in the T.O. mode (thermally opaque) based on occupancy.



There are 4 distinct areas in what I refer to as The Lake View room with 12 active panes of glass in these areas. Depending upon our use of those spaces will dictate the operating temperature and characteristics of the glass. If we're not using the area, then it will be allowed to roll back the MRT. If it is being used, the MRT will be maintained at a higher level. I am working on developing an inexpensive MRT sensor for interfacing into this very flexible control logic.



As the Winter rolls on, we continue to receive data from our "laboratory". One of the test modules is a passive solar module. For the first thirty days, we did nothing other than monitor space temperatures and glass temperatures with hourly readings from the Hobo Data Loggers. For the next thirty days, we are simulating the parallel input from a 48 volt solar array into the electric glass, so that we can see the influence of double induced solar gain (direct through the glass into the space and from eh solar collectors into the glass and into the space. At night, we do nothing but monitor the temperatures we were watching before.



Today, we add T.O. to the passive solar mix to see what effect maintaining the glass in the continuous T.O. mode does for human comfort. Our goal is to eventually find a home (Passiv Haus or Passive House depending upon which side of the pond you are on) whereby we can be placed, and possibly eliminate the need for ANY auxiliary heating system...



Now, you know what I've been doing in all of my "spare" time :-)



As contractors, we need to start learning about how to deliver COMFORT through heat radiating surfaces. Not just delivering HEAT. We are after all, in the COMFORT business, not just the HEATING business.



We also need to quit concentrating our efforts on the floors only....



ME

Brad White

Apples

I think we are munching the same apple, Icesailor!

We agree, sealing the air leaks is the simplest and most effective use of your time.



The quilt comment, I have see that borne out over the years. Clients would buy the roller track type window quilts, sit by the window and still feel a draft. Not outside air mind you, but reverse convection. Sealing the top and bottom to the casing helped, but only forestalled the inevitable.



Worse off, the quilts make the window surface colder and still pass moisture to the window. Puddle-City on the sill. I imagined little mice with skates having a pick-up hockey game and beating NJ. Oh wait, they did



The thing about glass- obviously the most conductive material in construction next to aluminum. Glass essentially has zero R value for discussion purposes. What glass brings to the table as a single pane is the ability to capture and hold air films, common to any assembly.



This typically accounts for an R value of 0.17 on the outside with a 15 MPH wind and 0.68 on the inside assuming still air. I would argue the outside film on glass is a bit less given it is smooth with lower friction, but dammit, I also have a life.



Add another pane and you do two things. The inside and outside air films remain the same, but you capture that interior air volume, presumably "still air", but also with additional interior air films on the facing panes. The wider these panes are apart, the more interior convection will occur and you lose the advantages of "still, motionless air" to a point. Still valuable, just not as good as a smaller tighter space.



When you have conventional double-pane with a 1/4" or 1/2" air space, convection is reduced but the thermal flux, the ability of reflected infrared radiation to bounce back and forth, is lessened also.



So, for my illustration purposes, I just wanted to show that two panes of glass held apart, have R values within range of one-another.

hot_rod

and the fin openings

need to be on the top and bottom

Mark Biro

Maybe patch up the door?

This is not, I think, quite what you are looking for, but have you considered using the 3M shrink film to add a layer to the existing door?



I looked into this when my parents built an addition that had FIVE patio doors.  Pretty, but profligate.  I found that adding (screwing) a wood strip at the bottom of the door would yield a single plane to which the sheet could be attached, with the normal 2-sided tape.  And 3M sells the film in large-format, "patio" sized kits.



It means, however, that this would either become am annual job (ugh!), or forsake the use of the door -- an easier option when there are 5 from which to choose.  ;-)