22 April 2017
Unless you're like me. I find this stuff very interesting. But if you're here to see pictures of progress on the house, you can skip this entry and wait for the next one.
So now that the piers and sill beams are done in the east wing of the house, it's time to answer several significant questions that stem from one fact and one desire.
Fact: We have to heat the house. It's required by code.
Desire: We want the house to be comfortable year round (yes, I hear the snickers from people who currently live in old houses). We'd like to minimize the draftiness and maintain a reasonable temperature, and more importantly in my opinion, humidity level in the house year round.
I turned my attention first to the crawl space. Should we have an open pier foundation?
I decided against this option for several reasons. First, as you can see in this example, all the plumbing is exposed. Not that it's terribly cold in North Carolina, but it does on occasion get cold enough for water supply lines to freeze. Second, the pipes are not attractive and detract from the period appearance of the house that we are trying to achieve (granted, some lattice around the perimeter would hide a lot of that). Third, the bottom of the house would be all sealed up. My background makes me look at this situation in terms of how easy would it be to fix a problem in or under the floor? How easy would it be to add new infrastructure or modify what's there? If a squirrel or other large rodent got up into the floor, how easy would it be to get them out? The answers to those questions is; Not easy.
Should we have a vented crawl space?
This type of crawl space is very typical in this part of the country and has been a standard building practice for a while. I decided against this option as well because I think it's important to control the humidity in the house and crawl space and there is a better alternative for doing that. Also the vents are problematic. They can break, get stuck open or closed, fall in or out, or have holes chewed through them. Traditional theory is that you would close the vents during the winter to keep the cold air out of the crawl space, then open them during the summer to let the damp air get out of the crawl space. In reality the vents rarely work well enough to stop all the air flow, and hot summer air in this part of the country is often more humid than the air in the crawl space. Ideally it's best for the wood structure in the house for the humidity to be kept fairly constant and at the lower to mid range of the scale.
I decided that we should try to get as close as we can to a sealed crawl space.
I like this choice because it makes it much easier to control the humidity levels. This article explains thoroughly the pros and cons of vented versus sealed. I would have access to the underside of the floor, all the plumbing, and all the electric. It also gives me the most control over air infiltration through the crawlspace and floor, which helps minimize the stack effect in the house. The stack effect occurs when warm air rises through a structure and leaks out through gaps around lights, vents, chimneys, holes in the framing for pipes and wires, etc. This creates a vacuum in the house which draws un-conditioned air in through gaps around doors, windows, vents, holes in the walls for pipes and wires, and the crawlspace.
There are all kinds of air leaks in an old house. Ours is by far no exception. But I believe that if I can seal nearly all of the air leaks in the crawl space and nearly all of the air leaks through the ceilings, then our house can be less drafty, and have lower heat loss compared to similar houses. There is a point of view that one should not modify the envelope of an old house at all, or only very little. The primary point being that the house has lasted 150 years precisely because it is not all sealed up. That the air flow in and through the walls and all the spaces of the house allows the wood to dry if it gets wet and helps maintain an equilibrium moisture content. While I agree with the basic premise, I believe that building science has advanced to the point where I can use that knowledge to try to control the airflow in the house rather than allow it to occur haphazardly and on the large scale it is now. Past attempts to make older houses more comfortable generally focused on insulating the walls primarily, the ceilings secondary, and ignored the floor. Little to no attention was given to air leaks except for the obvious ones around windows and doors. This can completely change the physics of the house, to its detriment. I agree with Bob Yapp and Bill Kimmel and believe that stopping as many air leaks as possible should be primary.
The next decision is how to control the temperature and humidity levels inside the house. We have 7 fireplaces. What about using those?
Unless you're like me. I find this stuff very interesting. But if you're here to see pictures of progress on the house, you can skip this entry and wait for the next one.
So now that the piers and sill beams are done in the east wing of the house, it's time to answer several significant questions that stem from one fact and one desire.
Fact: We have to heat the house. It's required by code.
Desire: We want the house to be comfortable year round (yes, I hear the snickers from people who currently live in old houses). We'd like to minimize the draftiness and maintain a reasonable temperature, and more importantly in my opinion, humidity level in the house year round.
I turned my attention first to the crawl space. Should we have an open pier foundation?
I decided against this option for several reasons. First, as you can see in this example, all the plumbing is exposed. Not that it's terribly cold in North Carolina, but it does on occasion get cold enough for water supply lines to freeze. Second, the pipes are not attractive and detract from the period appearance of the house that we are trying to achieve (granted, some lattice around the perimeter would hide a lot of that). Third, the bottom of the house would be all sealed up. My background makes me look at this situation in terms of how easy would it be to fix a problem in or under the floor? How easy would it be to add new infrastructure or modify what's there? If a squirrel or other large rodent got up into the floor, how easy would it be to get them out? The answers to those questions is; Not easy.
Should we have a vented crawl space?
This type of crawl space is very typical in this part of the country and has been a standard building practice for a while. I decided against this option as well because I think it's important to control the humidity in the house and crawl space and there is a better alternative for doing that. Also the vents are problematic. They can break, get stuck open or closed, fall in or out, or have holes chewed through them. Traditional theory is that you would close the vents during the winter to keep the cold air out of the crawl space, then open them during the summer to let the damp air get out of the crawl space. In reality the vents rarely work well enough to stop all the air flow, and hot summer air in this part of the country is often more humid than the air in the crawl space. Ideally it's best for the wood structure in the house for the humidity to be kept fairly constant and at the lower to mid range of the scale.
I decided that we should try to get as close as we can to a sealed crawl space.
I like this choice because it makes it much easier to control the humidity levels. This article explains thoroughly the pros and cons of vented versus sealed. I would have access to the underside of the floor, all the plumbing, and all the electric. It also gives me the most control over air infiltration through the crawlspace and floor, which helps minimize the stack effect in the house. The stack effect occurs when warm air rises through a structure and leaks out through gaps around lights, vents, chimneys, holes in the framing for pipes and wires, etc. This creates a vacuum in the house which draws un-conditioned air in through gaps around doors, windows, vents, holes in the walls for pipes and wires, and the crawlspace.
There are all kinds of air leaks in an old house. Ours is by far no exception. But I believe that if I can seal nearly all of the air leaks in the crawl space and nearly all of the air leaks through the ceilings, then our house can be less drafty, and have lower heat loss compared to similar houses. There is a point of view that one should not modify the envelope of an old house at all, or only very little. The primary point being that the house has lasted 150 years precisely because it is not all sealed up. That the air flow in and through the walls and all the spaces of the house allows the wood to dry if it gets wet and helps maintain an equilibrium moisture content. While I agree with the basic premise, I believe that building science has advanced to the point where I can use that knowledge to try to control the airflow in the house rather than allow it to occur haphazardly and on the large scale it is now. Past attempts to make older houses more comfortable generally focused on insulating the walls primarily, the ceilings secondary, and ignored the floor. Little to no attention was given to air leaks except for the obvious ones around windows and doors. This can completely change the physics of the house, to its detriment. I agree with Bob Yapp and Bill Kimmel and believe that stopping as many air leaks as possible should be primary.
The next decision is how to control the temperature and humidity levels inside the house. We have 7 fireplaces. What about using those?
Using the fireplaces with or without wood stoves would only address the heating part of this equation and would cost tens of thousands to implement since only one of the 7 fire places has a liner. This would also require having a significant source of firewood ready each winter. We're not trying to become homesteaders. We just want to live comfortably in an old house. Then we would need to add window air conditioners, or some other additional components to cool the house.
Putting window units on this house is something we simply do not want to do. The solution to that could be central air conditioning. But if you're going to put in the ductwork and air handler, why not make it heat and cool? So the answer is no to burning wood for heat. We'll get one or two fireplaces working just for the ambiance.
What about baseboard heating?
Electric resistance heat is one of the most inefficient means of heating a home. We would still need room by room air conditioning. So, no.
What about radiant floor heating?
If we were building new, I would absolutely put this on the short list. However I believe that this type of system loses effectiveness and efficiency when one tries to retrofit it into existing construction. Also, these systems do not provide a way to control the humidity levels in the house.
Another option that combines heating and cooling is minisplit units.
These systems appear to be efficient and don't require any duct work. But we decided against this option because we would have to have one of these head units in nearly every room, with a cable and hose line set running to each one from an outdoor unit. Really not attractive. We would be looking at at least 2 outdoor units plus 10 to 12 of these head units. Plus Minisplits don't appear to be as good at removing moisture from the air as central air systems are.
That leaves us with choosing a conventional central heat pump system, or a small duct high velocity central heating and air system. Two companies that I have found that make this are SpacePak and Unico. We're probably going to have two systems. One for the downstairs and one for upstairs. We have noticed a profound difference in temperatures between the two floors during the year we have been here. In fact, most summer days there would probably be no need to have air conditioning on the first floor, aside from keeping the humidity down.
The conventional heat pump system has the advantages of vendor choice (there always seems to be a large list of HVAC contractors in the phone book) and lower cost.
The SD/HV system has the advantage of easier routing of branch duct work to rooms that are hard to reach with conventional rigid ducts. We've been told that the initial cost is 30%-40% higher than a conventional central air system.
We haven't made a final decision yet between the two and are in the process of getting quotes from various companies.
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