Historical September–October 2011 article. Dates, prices, services and contacts describe the source period; current availability has not been established.
In response to Ursula Goodenough’s request in the summer issue of the Times, I thought I would share my experience and knowledge in energy conservation in our masonry homes.
I will also try to explain concepts in energy usage that even some professionals in the field tend not to know (or at least never tell you about).
I will start off by saying that there is no free lunch.
In order to make our old homes “energy efficient” real progress will not be seen without spending some cash. True, some small things can help trim the fat, especially if there is a single point of overabundant energy waste in your home. Doors and windows that do not shut properly in the dead of summer can be particularly wasteful since you are basically air-conditioning the outdoors.
But for the purpose of this article I will assume most people know enough to have addressed these issues and I will try to address more complicated matters that most people don’t really know.
We typically see big utility bills twice a year- with A/C usage in the summer and boiler/furnace usage in the winter.
The spring and fall are particularly cheap for us relative to other, more modern homes, and for good reason.
This is because our homes are masonry construction, with very thick walls (mine are 18” thick). Masonry, unlike modern materials (modern cheap building materials like wood and siding) has very high thermal mass. What is thermal mass? Let me explain in an analogy. Let’s say you are making cookies in the oven, and line the pan with aluminum foil.
When the cookies are done, do you hesitate to touch the foil that was just in the oven? No, because it has high heat transfer, or very low thermal mass.
On the other hand, if you cook food in a ceramic bowl at the same temperature, you cannot touch it without oven mitts for some time.
This is because the bowl has high thermal mass, just like our houses do. High thermal mass means is takes a long time to change the temperature of your walls. That means that the temperature inside our houses stays close to the mean temperature for the day, and in the spring/fall the masonry heats during the day and cools at night, but the temperature of the bricks stay about the same the whole day. You can see the obvious problem that arises with masonry homes in the summer and winteryou are continually losing heat in the winter and coldness in the summer since the mean outdoor temperatures are not desirable (too cold/hot), meaning you need to spend a lot of energy to heat and cool them. Modern houses do not rely on this principle, but instead use insulation to avoid this problem . Insulation works on a completely different principle . Instead of relying on thermal mass, insulation works by resisting heat changes.
In the earlier analogy, the oven mitt works like insulation by preventing the heat from interacting with your hand.
It acts as a barrier that prevents thermal transfer, and is typically measured in “R” values. Walls in modern construction typically have an R value of 10-20, and ceilings/roofs have a value of 30 or more. Our brick walls have an R-value of roughly 0.3/inch, so my 18” walls have an R-value of 5 (probably an over-estimation).
The obvious solution to this problem, then, is to have both insulation AND high thermal mass. I’m sure some people have completely gutted their homes and done this, but it is really not feasible for most of us. You would have to strip down to the studs (or in my case, frame-in walls since the plaster walls go right up to the brick) to add insulation.
To undergo this type of project you would need to be seriously committed to your home and plan on spending the rest of your life there, since it will cost a small fortune.
The ceiling/roof is another matter.
I bet most have had insulation added to the ceiling, and if you haven’t you should next time the roof is redone since that is where you will lose the most heat in the winter.
With knowledge comes disappointment. Many of the homes have had doors and windows replaced with “energy efficient” models, that have high R-values (a standard single-pane window has an R-value not significantly greater than 1-3).
We are told that these will save us money on energy costs.
However, if you understand the above concepts you will note that for most of us, these treatments will do absolutely nothing in the summer or winter, since heat loss will occur through the walls just as readily as the old single pane window (ok, it may do a little, but here is no point in an R-value greater than 5 since your walls will be less than that). So what can be done, besides insulating our walls? Since heating and cooling are basically inevitable in our hosing, we have to be smart about how it’s done. Ultimately, you can save money by upgrading to higher-efficiency models of boilers and A/C units.
Here is some simple advice regarding heating and cooling: 1. Cold air goes down and warm air goes up. Based on that alone, you will save money by placing your air handler (inside part of the A/C) in the attic rather than the basement. 2. Get a heat pump with your furnace.
These are like reverse A/C units and function in the winter when it’s above freezing outside.
They are a lot cheaper to run than a furnace, and come built in with modern A/C systems. 3. Stick with a boiler and radiant heat.
It is MUCH better than a furnace/forced air.
While a topic for another day, modern efficient boilers go up to 98% efficiency.
If you are considering replacing your boiler with forced air… stop right now. You will regret it later. 4.
On that note, upgrading your radiant system can save you a lot. Our homes had gravity-fed systems installed, which is why you may have 4” pipes running in your basement. That means that you have to heat A LOT of water. You can replace the system now with pumps and ½” pipe, significantly reducing the amount of work your boiler does. 5. Ductwork is the key for A/C systems. You need to have adequate return and air circulation for the A/C to run efficiently. Even a brand new unit may result in significant expenses if your ductwork is bad, since the fancy new motor will be pushing air against a wall, and be starved of return air. 6. Proper boiler sizing. Make sure you have the correct boiler size for the amount of heating needed for your home.
My home (2,010 sq ft. excluding the basement) needs 40-50,000 BTU (that’s british thermal units) per hour to maintain heat on the coldest day of the winter.
When I purchased the house, the previous owner had a 140,000 BTU boiler installed by a local company (that was continually fleecing them, again, the subject for another day). That is the car equivalent of driving during rush hour traffic in a Hummer with the pedal down all the way every time you accelerate. That means that the boiler system was completely inefficient and wasting vast amounts of energy.
I saved 50% of my heating costs by getting rid of that junker. You can get a company to do a heatloss estimation for you, and the procedure is tax-deductible, and anything you do to save on energy subsequently is also tax-deductible by the state of Missouri. 7. Do the math.
If your boiler is 84% efficient now (and, for argument’s sake, is properly sized), and you replace it with one that is 99% efficient, you will save 15% on heating costs assuming that is the only change you make to the system.
However, you have to take into account how much you spend on the unit.
If your net costs on the new unit is $5000, and your annual heating costs are $1000/year, it will take you 33 years to pay off the unit on your savings alone, and this transaction is probably not worth it.
If the unit needs to be replaced anyway it is another story. Last note, regarding basements. Ever notice that the basement is warmer in the winter and cooler in the summer?
There is a good reason for that.
The frost line in St. Louis is about 3 ft. That means that below that, the temperature of the ground is warmer. At about 5 ft., the temperature is about 60-65 degrees year-round. Also, the ground adds insulation. At 5 ft. below ground, the R-value of your stone walls is roughly 50. Incorporating the basement into the home living space can significantly cool your home in the summer and warm it in the winter, if done properly, and can significantly reduce heating and cooling costs. Of course, there are significant caveats to this approach, and may be the topic for another day.
If anyone is interested in more on this subject, feel free to email me at gbien@path.wustl.edu.
Originally published in The Times of Skinker-DeBaliviere, September–October 2011.
Read this article in the original newspaper issue.
Original source: SD_Times2011_09.pdf, printed page(s) 6; PDF page(s) 6.
