Category Archives: AC and Hydronics

Good & Plenum

One of the central elements of the redesign on the first floor is the bulkhead. It defines the dining/kitchen peninsula space and delineates the kitchen area from the good room. As noted in earlier posts, the bulkhead also serves a functional purpose as the east-west highway for infrastructure elements.

This post addresses the most intriguing feature of the bulkhead’s role in house infrastructure – serving as a plenum for return air to the AC.

The following series of photos documents the progression of the bulkhead from the early stages of framing to date:

In the photo below, the duct to the left is for AC supply; the duct on the right is for AC return in the rear of the house (there’s another at the top of the stairs). The plenum will serve to route air to this return duct.

The bad supply lines . . .

. . . and the good:

A plenum is a separate space provided for air circulation for heating, ventilation, and air conditioning typically provided in the space between the structural ceiling and a drop-down ceiling. In our case, the plenum will be an encapsulated space within the bulkhead to allow for flow to the return air vent, so we don’t have to put an unsightly, big-ass register in the ceiling (it would need to be 10″ x 10″). (The return air flow in this area will complement the return air register at the top of the stairs.)

Our plenum must be functional, but discrete, since it will be centrally located and we don’t want it to look like what it is. If properly designed, the plenum also will help to fulfill one of the design objectives of the bulkhead: define the dining space below by incorporating a raised area in the bottom of the bulkhead that provides visual interest and a home for pendant lights. This raised area would be part of the bulkhead regardless of HVAC needs and could be executed very simply in order to meet the design objective, but the return air flow function of the plenum gives us the opportunity to address both form and function goals with a single, elegant solution.

Here’s the plan that Natalie developed to meet the need, based on a design concept from the owner of the GC (who’s also an architect) one morning during a site visit:

The first step in executing on these drawings was to extend the return air duct and add a 90-degree turn, so it opened on the bottom. The next step was to surround the duct opening to create what would be the top of the plenum. Here’s how it looks at this point:

However, something’s clearly amiss. The pendant light junction boxes aren’t distributed equally, as a result of the location of the vent:

It turns out that the guys were, um, looking at the plans upside down when they started to built this (in the top-down view on the right side of the drawing above, the short end on top (west side) was mistakenly considered to be on the bottom (east side)). The vent actually fits perfectly between the second and third junction boxes if they’re evently distributed.

The problem was easily corrected – here’s the correct configuration (evidenced by the hanging electrical wires), after this has been addressed and after drywall has been installed:

The bulkhead is becoming less intrusive and more an organic part of the floor after the drywall has been primed and the wood trim has been added at this stage:

Now for the functional design details. The plenum needs to allow 100 sqare inches of air flow to allow the return to perform properly, but the “floor” of the plenum (which will be the top of the raised area of the bulkhead) needs to be attached to the already installed plenum ceiling, and we don’t want the return air functionality to be evident from the dining peninsula, so we can’t have holes in this floor. The solution is to have air flow around the sides to enter the plenum. To attach the floor of the plenum to the ceiling and still permit this flow, crenelated trim is used:

Here’s a better view to show how air will flow around the sides and through the holes to enter the return air vent:

To hide all of this, the sides of the bulkhead are trimmed out to 1″ below the beadboard, and the trim is turned on the bottom to extend 6″ into the center.

As a result, you can no longer see the sides that have to be left open for air flow, and the whole unit now appears exactly as it should from a design perspective. The dining peninsula will be directly below this raised area, which now conveys the visual interest needed for this element.

In the photo below, cellulous sound insulation has been shoved into every nook and cranny of the bulkhead around and on top of the plenum and the ends of the bulkhead have been sealed up with trim. Installation of crown molding also has begun.

As noted in the kitchen design post, cabinetry extending 24″ out from the party wall will occupy the area under the right side of the bulkhead in this photo, which will come within 6″ of the raised area. The dining peninsula will extend to 6″ to the left of the raised area, and the remaining space will serve as the passageway between the good room and the kitchen area.

Here’s a parting shot of the completed bulkhead after the contentious crown molding has been installed:


A Final Look at House Infrastructure – First Floor

At the front of the house, there’s a gang of switches, and the electricians had to demo the plaster in this area to run the new wires. All of the casing around the doors and windows has been removed, as well . . .

Our powder room wall is more infrastructure pipes and wires than it is framing . . .

To the south of the powder room, the pantry walls house plumbing and electrical, including bundles of electrical wires running up the end of the new wall from the electrical panel below to supply the second floor.

Rough-ins for the south end of the kitchen:

And electrical, gas, and the hood vent to support elements on the west wall of the kitchen:

The kitchen walls also house hydronic infrastructure elements. Here, the red, radiator supply and return lines for the master bedroom travel up the kitchen bump-out wall:

You can see a 360-degree view of the first floor (in the gloom resulting from boarded-up front windows) at:

As with the second-floor walkthrough videos, this one does nothing but reinforce the exceedingly geeky interest we have in the renovation details. However, it does provide an interesting view of the house infrastructure elements in a different context.


Posted by on May 15, 2012 in AC and Hydronics, Electrical, Plumbing


A Final Look at House Infrastructure – Second Floor

The exposed-infrastructure stage of home renovation is drawing rapidly to a close. Insulation and drywalling activities are looming (they’re actually already here, it’s just that our posts are woefully behind), and it’s time to take a final look at the exposed house elements before they’re forever entombed.

On the second floor, there’s a mess of plumbing, electrical, and mechanical elements in the utility closet between the hallway and the master bedroom. The placement of the air handler on the top floor (consistent with the pre-reno house) helps in AC distribution and minimizes the distance between this component and the compressor directly above it on the roof.

The utility closet also will house stacked, front-loading washer and dryer. The blue spot on the floor in the photo above is one end of the emergency drain line that exits directly from the side of the house in case the washer has an issue. Rough-in electrical and plumbing occupy the south wall of the utility closet for the washer and dryer.

The wall between the two upstairs bathrooms house all of the plumbing supply and drain lines and electrical rough-ins. All of the extra wiring supports subsequent pendant lights in the master bath and sconce lights in the guest bath.

The plumbing rough-in for the two bathrooms is identical: supply lines for flow control valves and fixtures for shower heads and hand-held showers and a thermostatic controller that supports both.

Lots of electrical rough-in elements surround the bathroom framing:

In-line fans mounted above the guest room rafters support both bathrooms. Because of the floor-to-ceiling glass doors on the showers, we need to vent moist air, and these remote fans take care of this nicely. The GC wanted to install routine bathroom ceiling fans, but this approach supported both showers and bathrooms, and were super efficient, so we went with this approach, spec’d by our first architect.

A subsequent picture of the fans appears below, after the insulated vent lines have been attached.

Electrical rough-in also had to contend with solid brick exterior walls in much of the house. The result was a collection of new pockets in the brick to accommodate electrical outlets that will poke through the baseboard in the guest room, pictured below, and all over the main floor, the subject of the next post.

You can see a 360-degree view of the south side of the second floor at:

And you can see the same for the north side at:

Both links are dorky as hell, but highly informative!

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Posted by on May 15, 2012 in AC and Hydronics, Electrical, Plumbing


Basement Utilities Reach Critical Mass

One of the advantages of our basement demolition and excavation efforts was to clear out decades of plumbing, hydronics, and electrical (especially electrical – we had three generations of technology down there, from some original knob-and-tube, to wire conduit, to Romex), and start anew with a basement utility hub that wouldn’t eventually burn down the house.

The additional benefit of the excavation of the southeast crawlspace, specifically, was to allow the boiler (which would supply hot water to the radiators and heated floors), the hot water heater, and the electrical panel to be consolidated in one area of the basement. This would allow maximum utilization of the remaining area. This crawlspace area was barely usable in the pre-reno house. Some pics of the basement before are provided below.

Here’s the old boiler and hot water heater, located on the west side of the basement (really, the only place they could be, due to the limitations in this area):

This is an even better picture of the mayhem that lay dormant in our basement. Looking through the doorway, you’ll see the old electrical panel, located in the quasi-exterior area in the basement. Note the crawlspace area between the door and the panel – previously of limited use, this will be the home of the new home utility hub. The plumbing stack in front will remain where it is (as seen in

Regarding the tangle of old wiring, plumbing, and hydronic elements in the old house, check out this action, which includes hydronic lines to nowhere that were capped off when radiator locations changed during previous renovations:

All of this came to a satisfying end with the demo work. Our contract with the GC specified that everything down here would be eliminated and reinstalled and replumbed and rewired anew . . .

After demo and reconstruction of the expanded basement (, the first step of our new power plant installation was arrival of the boiler and hot water heater. The boxes obviously contain these items; the equipment already mounted to the block wall is the manifold for the hydronic lines, which we’ll see later:

These elements will actually be located in the space that previously was occupied by crawlspace, so, bonus in space utilization, eh?

To the right of the boiler and water heater will reside the “heavied-up” electrical panel (from 100 to 200 amps) to support more electrical. At this point, it’s just the termini of a bunch of electrical cables.

Here’s a photo of the water heater and boiler after initial installation. There’s a lot more to go before this area is complete, including installation of the electrical panel, which is still AWOL at this point. The grey canister is the new expansion tank, which previously was a large, green drum about 5x the size that hung from the joists above the work bench. The old tank needed to be drained periodically, and so we’d have to screw a hose onto it and run the hose across the basement to the utility sink. The worst part was that there was no venting on the drum, so the water that had built up would drain for hours. The new expansion tank has a rubber bladder inside that contracts when water needs to escape from the hydronic lines, then expands to expel it back again when the expansion need abates. No muss, no fuss.

In the photo below, the electrical panel has been installed, as well as additional electrical lines (and the underfloor heating at the back of the house, which we’ll see in more detail). Jim, the lead for the mechanical sub, is doing some install work down here the day the picture was taken. (They did a spectacular job with installation of both the hydronic infrastructure and the AC components.)

Another new development at this stage is installation of the electrical panel (sans connections).

This is what’s lurking behind there – a manifold to route hot water from the boiler to three zones in the house. At this point, there’s only a few lines coming off it, but it’s going to get really crowded.

The three climate zones in the house are:

  • The second floor, heated by salvaged radiators in each of the two bedrooms, as well as under-floor electrical heat in the two bathrooms,
  • The first floor, heated by under-floor hydronic heat in the vestibule and kitchen, and by two small (really, really small) radiators in the powder room and the area at the top of the stairs the basement, and
  • The basement, heated by radiators in the office area and in the unfinished area.

In addition to controlling the radiant heat (as well as the AC) via thermostats on each floor, there are failsafe controls directly on the trunk lines for hot water heading into each zone. These three brass, manual controls can be seen on top of the copper pipes in front of the PVC drain line and above the expansion tank.

The red tubing feed two types of radiant head elements – radiators (before which they are connected to copper pipes) and under-floor heating. In the photo below, you can see some of this latter heating approach.

Here’s a view of the actual heating elements. Insulation beneath the radiant elements will be installed later, with a reflective side against the metal plates.

Unlike the new basement area, where we had brand new, virgin framing to work with, the under-floor heating in the front of the house had to be run through existing space. The guys had to rip out drywall and install the radiant plates and hydronic lines above the built-ins, which we’re retaining:

This is pretty much the apex of hydronic lines. The red ones heading up in the photo are supply and return lines for the master bedroom radiator and under-floor heating in the kitchen.

Late in the infrastructure game, the gas lines were finally run. We had to upgrade our meter to a high-pressure line to accommodate the additional appliances. Gas will be required in the renovated house for the following:

  • Hot water heater
  • Boiler
  • Dryer in the basement
  • Stove
  • First-floor fireplace
  • Master bedroom fireplace (future)

Similar to the manifold approach to distribute hot water for radiant heat, a manifold was installed to distribute gas to the appliances throughout the house:

The yellow gas lines shortly thereafter began to infiltrate the basement. Here’s a shot after the lines were run off the manifold. In addition to the new lines, insulation in the first-floor joist bays has been complete at this point. The area’s dense with equipment, electrical lines, hydronic lines, and gas lines, now that the basement utilities have reached critical mass, but we’re happy it’s all in once place, compartmentalized from the rest of the newly excavated area (which will allow for storage of more bikes, of course . . .).

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Posted by on May 7, 2012 in AC and Hydronics


Save the Bay(s)

As seen earlier (, one of the several dramatic steps to our renovation was our reluctant removal of the original second-floor joists across three quarters of the length of the house. The joists were pocketed directly into the brick exterior walls, and were perfectly sound, and so we really hated to remove them. However, the 1925 joists ran in an east-west orientation (from side to side in the house, rather than front to back). To route house infrastructure elements for our open floor plan design, north-south orientation was needed.

So, most of the old joists needed to go. They were replaced by the north-south oriented 2x10s that were supported by strategically placed glulam beams. The one area not affected by the new framing was the floor under most of the guest room at the front of the house. There’s no plumbing there (although there will by hydronic supply and return pipes supporting a radiator, as you’ll see), and we were able to develop a workaround to route the AC supply vents there ( As a result, leaving the original joists in place at the front of the house was a way to conserve costs (one of the precious few, we’ve come to realize).

Mechanical, plumbing supply pipes (copper, not PVC . . .), plumbing drain pipes, and electrical for the second floor all needed to live somewhere, and that somewhere would be the “bays” between the new joists installed during the renovation. This post provides a Cliffs Notes version of installation of the house infrastructure elements by way of the evolving bay landscape seen from below, on the first floor.

The picture below shows the joist bays after framing has been completed, but before any infrastructure elements have been installed. The triple beams and odd framing on the left side is there to support the showers on the second floor.

In the picture below, elements of the mechanical system begin to appear. One of the vents is orphaned in a bay on the far side of the bulkhead.

The vent is now connected to the AC supply line in the bulkhead, and has been joined by PVC drain lines.

In this view of the bays to the south, the mechanical and drain lines have been joined by copper plumbing supply lines. Note the framing to the right – the original beam arrangement had to be removed and reconstructed after the plumber started doing his thing, and they realized it would not allow pipes to be routed properly.

Electrical has now joined the other elements at this stage.

And what’s the electrical for? Among other things, the recessed lighting in this area, which has been installed at the point this picture was taken. The rearrangement of framing under the showers also solved a lighting design issue. With the original framing, we were not able to install lights in the locations called out by the plan. With the new framing, this obstacle was removed, and both plumbing and lighting could be implemented correctly.


We Just Need to Vent a Little

The interior framing is complete, so house infrastructure installation is on deck. The infrastructure components include mechanical, plumbing, hydronics, and electrical. They get installed in that order, since the vents for the  mechanical are the largest component, then the plumbing drain lines, then plumbing supply lines, then hydronics, then electrical cables. It’s a lot easier to route 3/4″ copper pipe around already-installed 10″ AC vents than trying to fit these vents in between framing and plumbing elements if they were done in the reverse order . . .

The mechanical systems in newer houses typically includes an AC/heat pump that provides both cooling and heating through the same vents. Our house originally had radiators for heat (requiring a hydronic system to supply and return the hot water); separate AC vents and a mechanical system was added later to complement the radiant heat. Once you have a house with radiant heat, you never want another system – trust us. So, we’re replacing and optimizing this system. This post focuses on installation of the air handler and air conditioning vents. Future posts will cover the other infrastructure elements as they follow, in order of declining diameter.

The first thing to get installed was the air handler at the top of the stairs on the second floor. The guys from the mechanical sub started to set things up on a Tuesday:

Vent components on the second floor ready for installation. The insulated units go above the rafters on the second floor, where the environment won’t be conditioned, like the interior spaces. Although we’ll be doing foam insulation, which has a wicked bad R insulation factor, and a white membrane roof, the space above the rafters still will be hotter in the summer than the rest of the house. (Plus, code requires this, so, insulated vents it is.) The bare metal vent will be installed between the second and first floors to supply the first floor with conditioned air in the summer.

AC terminal units awaiting installation. These will branch off of the larger vent units shown above.

Insulated vents get installed in the master bedroom, awaiting registers during later stages of construction.

Venting in the master bedroom. This is routed directly from the air handler, so we’re hoping it won’t freeze us out in the summer . . .

Venting over the rafters in the guest room from the air handler to the south (right). Although the vent in the foreground serves the guest room, there’s another behind with black insulation that leads to a ridgid vent pipe in the northeast corner of the room.

The articulating, insulated vent at the back leads to a rigid vent which heads downstairs . . .


. . . to this articulated vent and opening for a register in the vestibule ceiling on the first floor. The reason for this routing is that, because we left intact the original, east-west oriented joists between the first and second floors at the front of the house, we can’t tie the AC in this area to the main supply line that you’ll see below.

This vent-o-vestibule is just a side show for the real venting process for the first floor. The supply vents from the air handler at the top of the stairs on the second floor immediately split into two major trunks. One heads up through the rafters and supplies the second floor; the other heads immediately down through the floor above the powder room and supplies most of the first floor. Here’s a view of the complex routing of supply and return vents above the powder room, as they penetrate the second floor subflooring into the bays between joists on the first floor. From top to bottom, you see the major return vent from the first floor, the major supply vent, and a branch line from supply to a register located in the ceiling between the powder room door and the stairs to the basement:

From the powder room, the supply vent has been installed within the bulkhead created by the glulam beams:

At this point, both the supply and return vents have been run through the bulkhead. The former will then branch out east and west through the bays between the joists to registers in the first-floor ceiling (ignore the drain lines, for now – we’ll deal with that bit of infrastructure in a future post).

From the major supply vents in the bulkhead run branch lines to openings registers in the kitchen. First the target openings:

Then the rigid vents connecting them to the trunk in the bulkhead:

The air handler on the second floor after installation. One return register will be located here, at the top of the stairs (you can see the opening here). Another will be located near the dining peninsula on the first floor (stay tuned for the specifics – could be interesting).

Here’s a view of the installed air handler from the south:

The cooling lines from the air handler head through the roof to the compressor, which will be brought in after the new membrane roof has been installed:

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Posted by on April 8, 2012 in AC and Hydronics