Hello, Just got ourselves into an 1865 4-story brick mess of a house. We're trying to be as green as possible -- on a shoestring budget, as we find more wrong every day. The house is approximately 2400 square feet. Also, we have exposed all of the brick inside and the entire house is pretty much a shell (no insulation). Will be rewiring, replumbing, etc. Have a pretty new Lennox natural gas powered boiler with Input: 150,000 BTU/HR, CGA Output: 123,000 BTU/HR, Steam 15 PSI, Water 50 PSI. This formerly powered a very old baseboard hydronic system. I was told that it could be used for a new in-floor system, so we want to keep it. Three items of note: the attic (guest area) had no heat source before. Secondly, we're pouring a slab in the basement (now excavated to dirt), we are hoping to pour a thin (2") slab on the main floor also (now old wood flooring). My questions: What is the smartest/most cost efficient way to separate the zones between electric and hydronic? (Everything's torn open, so we have easy access to install the hydronic tubing in between the floor joists. ) What is an affordable electric system? They all seem very expensive. Does anyone have an opinion about Radiantec in Vermont (for hydronic)? Thanks in advance.

I don't have direct answers to your questions but offer the following:
1. Place the most effective insulation you can before closing up the walls - probably foam for best sealing and R Value in the least thickness.
2.Don't pour a slab on the wood floor unless you verify that it is structurally strong enogh to hold the weight. Most of these old houses don't even meet current span requirements for a wood floor let alone an additional 2 " slab.
3. Try to find a way to insulate well enough that your current boiler is adequate so you don't have to add any electric zoned areas.

Thanks for your reply. Just found out that our boiler is not large enough in its output for all four floors of the house... I was told that we'd need 166,000-170,000 BTUs for the square footage. In light of that, would there still be a way to super-insulate in the attic and any walls we do decide to recover (while keeping the exposed brick in the majority)? We do know that we have to reinforce with posts and beams (and footings) to compensate for the weight of the concrete floor.

What climate are you in, cold, moderate, warm? This will make all the difference in how you approach this project. We will be shooting in the dark with any comments until we know this. Also, describe more completely the brick wall construction, i.e., how thick, how many layers of brick, any air gap between them, etc. Is the underside of the roof exposed? Given the right approach to this project, your boiler could end up being oversized. Is the square footage the footprint, or the total floor space of the living area? If the latter, what's the size of the house? What sort of windows do you have? Are you planning on replacing them? Does four floors include basement and attic? So far, what info you've offered and the questions you've asked don't much more than scratch the surface. :-)

Thanks.

Phew, I was worried about giving too much info! Here goes: The house is in Poughkeepsie, NY. We've just moved here, so I don't know how the weather really is year-round. The exterior footprint is 25x30'. The interior dimension is about 23'4"x28'4". We have gutted the entire interior: all interior walls, ceilings are open, plaster has been removed from all brick. The house entry (front) is the main floor, then 2nd floor and (formerly) finished attic. In the rear, the basement is daylight -- above grade one full story. So, the house stands 3 stories to the street (with stand-up crawl-space under porch) and 4 stories to the rear. The attic ceiling is open to the rafters (now). There is an extra course of bricks in the basement (3-deep) with an air gap between. The remaining height of the house is 2 bricks deep with air gap. The windows were already replaced by the former owner. They are Simonton double-paned vinyl (sigh). We are pouring a slab in the basement (390 sq. ft. worth) and installing hydronic radiant heat in it. The main floor and second floor will also be in-floor radiant heat. The attic will be either electric matting radiant heat or baseboard radiators (prefer the former if we can afford). Most all of the exterior brick walls will remain exposed, we hope. Hopefully not foolhardily, I ordered the hydronic radiant heat system yesterday (d.i.y.). Thank-you for your interest and questions.

I'll write more later today, but one thing before you pour the basement slab, insulation. If you want the basement to be warm and usable put a minimum of 2" Styrofoam board under the slab, more is better. You haven't mentioned doing this so that's why I point it out. DO NOT put down the slab without insulation under it. Otherwise you'll be needlessly sinking money down the ground.

Kinda like what a stickler for details you are... Planned anatomy of floor in basement over (existing) dirt: 1. gravel (or Item 4 crushed stone) 2. foam board insulation (will probably opt for 4") 3. vapor barrier 4. rebar 5. radiant tubing 6. 4" slab Thanks, again.

Thanks for the info. You'll want the vapor under the insulation. Consider using fiber reinforced concrete and do away with the rebar. It's easier, cheaper, and plenty strong enough. Fasten the pex tubing to the foam board with special staples or holders that screw into the foam. I don't recall the names of them but you should be able to find them. One place for info is ZurnPex.com.

Poughkeepsie, NY is somewhere near the border of climate zones 5 & 6 in the moist region of the country. In other words, you're in a cold, damp climate when it comes to heating.

Now, the exposed brick. Maybe you already have done this, but think really, really, hard about leaving the brick exposed. The single biggest reason you shouldn't leave it exposed is heat loss. Those brick walls will be cold in the winter. Since you're using hydronic you surely must have a good understanding about the radiation part of radiant heating. Well, it applies to cold also. Those cold walls will suck heat right out of the floor, the furniture, the interior walls, and especially you and your family. I had a house just south of Pittsburgh in the early 70's. The first floor was clay tile construction with stucco on the outside and plaster on the inside. In the winter you could just feel the heat radiating from your body to the cold walls. I think there are two possibilities that may make it feasible to leave the brick exposed. If you have, or can apply, a good insulated siding system on the outside and/or if you can fill the air gap between the layers of brick with foam you may be able to cut the heat loss down to a manageable level. But to have a really good energy efficient home you should consider a stud wall inside the brick wall sealed tight and stuffed full of insulation.

Another thing to consider. If you have a high heat loss your hydronic system needs to pump out that heat. You may run into a problem with having to either have your tubes close together, like maybe 6" or closer, in order to keep the temperature and water flow rates reasonable, or you may end up with uncomfortably hot floors as the system tries to pump out the heat necessary with higher temperature water. Another option for keeping the brick is forget the in-floor heat and place radiators or baseboard heaters on the outside wall. That way you can really crank the heat up and warm up the air that sweeps down along the wall.

Seal the dickens out of the house. Since you have the interior exposed now is the time to look for every crack and hole where outside air can come in, and seal it. Consider foam insulation on the underside of the roof. The heat loss through an insulated roof and sealed and conditioned attic is about the same, or less, than through an insulated ceiling under a vented attic. When you seal the house really tight, you will need to add a mechanical ventilator. A heat recovery ventilator will keep you from pumping too much heat outdoors.

Have you done, or had done, a heat load calculation for your house? If not, you really need to do it. A good HVAC contractor can do it for you and give a listing of heat losses by floor and room. If you want to do it yourself get HVAC-Calc. You can use it for 2 months for $49.95. I've used it and it's pretty good but doesn't provide nearly as much detail in the output. But you can input different scenarios for wall construction and insulation and get a real good idea of how much heat you'll lose with inadequate insulation. You then need to convert the heat load room by room into the tubing layout. Tubing layout requires considering spacing, tube diameter, water flow rate, and water temperatue. There's a limit to each one.

If you do end up changing out your boiler, and have yard space available, consider going to a geosource heat pump. That way you can cut the cost of heating in terms of Btus of energy you buy, to about 1/3 to 1/4 of the total heat load.

Whatever you do, try to stay away from electric heat, including electric radiant mats. Electricity is just about the most expensive energy source there is, unless you run a heat pump with it.

That's enough for now. If any of this is old hat and you've already thought it all out, please say so and forgive me for going overboard. You did ask for advice, and my approach is to make sure the cake has been baked properly before we start discussing the icing! :-)

For more info go to BuildingScience.com. There's a lot of good info about building for cold climates there.