Soundproofing

Not every home has a media room. This room is dedicated to enjoying video games, shows, movies, and music. It can handle an intimate group — just the two of us — or a larger group — a Rock Band party. One way a media room differs from a family room with a TV is the extra effort put into isolating it from the rest of the house. As much as possible, activity in the media room shouldn't disturb the rest of the house.

Basics of Soundproofing

Let's start with a quick review of sound. Sound travels via vibrations in air and solids (and liquids, but houses generally aren't built from liquids). When a sound wave hits a wall the wall will vibrate, which will cause the air within the wall to vibrate, and transfer sound to the other side of the wall. The sound wave vibrates the studs in the wall, providing a second path to the other side. There are many ways to decrease the amount of sound transferred:

• Decoupling elements: If the drywall on the inside of the room is not directly connected to the outside of the room, then there will be no solid pathways to transfer sound.
• Absorption: Loose material in the empty spaces of the wall help absorb and deaden the sound attempting to travel through the air cavities in the wall.
• Adding mass: Heavier materials require more energy to make them vibrate. By adding mass to the walls, more of the energy from the sound will be absorbed by the walls, and less energy will be available to transfer through the wall.
• Damping: If it is more difficult for the wall to vibrate in the first place (i.e., it doesn't respond as much to the sound waves), then less sound will be transmitted.

This information was summarized from a more in-depth article from the Soundproofing Company.

The Walls

The most important element of a soundproof room is the walls. In the world of soundproofing, there are many wall options and many trade-offs. We chose a solution that is simple and cheap.

The lower part of the walls are formed by the concrete foundation; the added mass of these walls help to reduce sound transmission.

We added soundproofing insulation to the interior walls. The materials and labor for the R-13 insulation was cheap, so we insulated all the interior walls in the house. This will help absorb sound traveling through the air cavities in the walls.


We looked at several wall damping solutions for the media room. A popular solution is Green Glue, a compound put between two layers of drywall to dampen sound. The material is cheap, but it does require a second layer of drywall and extra installation time. Because is is inexpensive and not difficult to install correctly, it is popular in do-it-yourself solutions.

A second option is QuietRock. This is an all-in-one damped panel that is installed in place of drywall. Installation is exactly the same as drywall, but the material costs are more expensive.

Another option was Resilient Channels. These are attached perpendicular to the studs, and drywall is attached only to the channels. This allows the drywall to flex a bit and dampen more of the sound. It also provides decoupling from the studs. The channels are cheap, and installation is not too much more complex than just drywall. Care needs to be taken to prevent the screws connecting the drywall to the channel from touching the studs (this would prevent the flexing and decoupling of the drywall).

We chose channels because of the price and because the installer is familiar with them. Sound isolation clips can be used with some kinds of channel and provide extra isolation, but they add material and labor expenses. We decided channels should be good enough for the level of soundproofing we want. If we want something more, adding Green Glue plus a second layer of drywall is a relatively straightforward addition that we could do later. It wouldn't require removal or remounting of the existing drywall; it is simply a second layer added on top of the existing drywall and channels.

The Details

Walls are the most important part of soundproofing the room, but the details are also important. The mass of a solid core door prevents sound from easily travelling through it. A gasket around the edge of the door provides a strong seal against the frame when closed, and less sound is able to travel through the gaps around the edge of the door.

We avoided can lights because those allow sound to travel through the ceiling. Surface-mount lights allow a solid layer of insulation in the ceiling and nearly unbroken drywall on channels.

The attachment points of the projector mount and screen can negate the advantage of the channels, if screwed into the studs through the drywall. The projector mount is mounted directly to blocks in the ceiling. The drywall will be installed around the mount and a bit of sealant will provide a flexible interface between the drywall and the mount. The screen should be able to attach directly to the drywall without going through to the studs. It is heavier than the projector but spread over a larger area.

Carpet is an easy flooring choice. It provides extra soundproofing, is comfortable, and provides better acoustics. A hard floor would reflect more sound.

Sound travels well through the reflective walls of vents, but fresh air is critical in a tightly-sealed room. We are using a supply and return to the HRV system to provide fresh air into the room and evacuate the stale air. The supply will be tucked into an open portion of the closet, while the return will be in an enclosed portion of the closet. The closet should help muffle the sound that makes it to the vents. They both go to the HRV, which we assume will not transfer too much sound into the other ducts attached to it. Bends in the ducts will also help absorb sound.

Overall, not a lot of changes were needed to provide extra sound isolation in the media room; we mainly had to spend time considering details. From that, we should get a reasonable level of soundproofing without too much extra cost.

Electrical & Wiring Design

One of the areas that requires a lot of design work is wiring: the electrical system and other wiring such as phone, cable, and data connections. It is important to get this right before the walls are sealed up because it is difficult to modify later. It is the system that has the most end-points, will have the greatest effect on day-to-day life, has more flexibility now than it ever will, and has had the least design or input so far.

Outlets near floor in living room. One for data, one for electrical.

Outlets
The electrical system includes the lighting, electrical outlets, and switches. We'll cover lighting separately — it involves a lot more than just wiring.

The electrician spaced the electrical outlets about equally around the walls. Other than a few specific requests, we trusted his judgement and code for the exact placement. On the main floor, our builder had the electrician turn the outlets horizontally and place them close to the floor for a cleaner look. Upstairs in the more functional rooms, outlets are at a standard height and orientation for better accessibility. In a few locations where we know we will have desks or counters, the outlets are just above or below desk height to provide easy access for equipment.

Main breaker panel (rather full)

Other wiring
The rest of the non-lighting electrical wiring is for appliances. Nearly everything in our house is electric, including the HVAC system, water heater, sump pump, dryer, oven, and now the cooktop. We pre-wired for an electric car charger in the garage — this was the biggest cable, up to 100 amps. The oven/microwave combo and cooktop require 50 amps each, the dryer, water heater, and sump pump each use 30 amps, and each of the two exterior heat pump units use 15 amps. This adds up to a large potential load on our electric capacity. Most of these items won't run at full load most of the time, and many will run rarely. A demand-weighted load calculation showed that we should be fine with the standard 200 amp service common in new construction.

Kitchen outlet with phone (blue), ethernet (grey),
and twine for pulling cable through the conduit.

Communications
The area we had the most input on was the communications wiring. We believe cable and phone connections are becoming obsolete, so we only added a few. We have one phone connection in the master dressing room and one in the kitchen (where we're planning a communications center). We added one cable connection in the living room and one in the media room. These should cover most important use cases.

Main ethernet panel with conduit

Our dominant communication technology is digital data streams. This was where we focused most of our attention (and money). Wireless LAN is nice for quick access from anywhere, but it is not as reliable or as fast as ethernet. We have a wired access point in each major area. WLAN or long cables allow access near that endpoint. We specified cat6 cable so it will be usable for as long as possible. Upstairs, we have an endpoint in each of the secondary bedrooms, one in the master dressing room, and one in the laundry/craft room. On the main level, we have one in the kitchen, one in the living room, one in the office, and one in the garage. The closet in the media room will be the center for both media equipment, and our computer connections and servers. All of the ethernet runs from the upper two levels end at a panel in the media closet.

Living room with conduit
for future cabling

Even cat6 ethernet cable will eventually be replaced by something better. To provide future flexibility, conduits run from the media/server closet to locations throughout the house. This is tubing in the walls with a string run through it. In the future, we will be able to pull the latest cable (such as fiber optics) through that tube, allowing us to provide hard-wired access to the main locations in the house.

Crawlspace with several conduit endpoints

Conduit is harder to run and costs more than ethernet cabling, so we limited ourselves to three conduits per level. The upper level has one for each second bedroom, and one in the master dressing room. The main level has one in the kitchen, one in the living room, and one in the office. To make it easier to pull a cable through, the conduits go roughly straight down and end in the crawlspace; one larger conduit connects the crawlspace to the server closet.

Projector mount with conduit and electrical

We have a short conduit within the media room that runs from the media closet up to the middle of the ceiling, where we have a mount point for a projector. This allows us to run a video cable such as HDMI directly from the source equipment up to the projector in a convenient and concealed manner.

Sound
Wireless speakers are good enough for ambient music, so we limited our speaker wiring to the media room.

Two subwoofer coax cables run from the media closet to opposite corners of the room for flexible subwoofer placement. Speaker wiring is run from the media closet out to eight locations in the room: three in the front, three in the back, and two on the sides. Not all of them will be used right away, but we wanted to support whatever future formats might specify. The side speaker wires aren't even ended at an outlet; there is just some extra cable in the wall which could be used in the future. The rear connections end at the floor so that they can be run up a speaker stand. Extra cable was left in the wall higher up to support wall- or ceiling-mounted speakers.

Rear speaker wiring with outlets near the floor
and extra cable above

Security/automation
The final wiring is low voltage wiring for a security system. It also enables the much more interesting possibility of home automation. Door sensors and motion sensors can be triggered for security or automatically turn on lights when someone enters a particular area. Wiring for a security panel can be used to install a touchscreen for central control. Some extra wall switch boxes were installed to support programmed control of lights at several main locations within the house. All the wiring for these systems was run downstairs into the server closet. At our discretion, we can install a panel that connects everything up and provides security, automation, or both.

Green Home Tour

Our house will be participating in the Seattle Green Home Tour this coming weekend! Our in-progress house will be open Saturday and Sunday from 10am-4pm. One or two of the finished houses in the development may be participating, too. We'll be hanging out there for a while each day, and would be happy to give a tour and talk about anything you're interested in.

For address and more information, check out the page about our site.

Heating & Cooling

"Can we have multiple heating zones with this setup?"

What far reaching affects this innocent question had! Our original plans for an HVAC system were fairly typical for a new home in the US: single-zone, central-air, powered by an efficient gas furnace with an attachment point for a future air conditioner coil. You can add zones to variants of this system, but it becomes increasingly complicated (and expensive). Yuval suggested that we look at heat pumps.

What is a heat pump?

A heat pump uses condensation and evaporation of a refrigerant to heat or cool a space. Air source heat pumps use the air as the energy source/sink. It doesn't take much to get a feel for how heat pumps can heat a space:

• Evaporating the refrigerant transfers energy from the air into the refrigerant. The loss of energy leaves the air cooler.
• Condensing the refrigerant transfers energy from the refrigerant into the air. The addition of energy leaves the air warmer.

This may make it seem like heat pumps would require the space where the energy is coming from to be warmer than the space where the energy is going to, but this isn't the case. The heat source only needs to be warm enough to transfer energy to the refrigerant, and the heat sink only needs to be cool enough to accept heat from the refrigerant.

Refrigerators and freezers illustrate this well. They use a small air source heat pump to make cool spaces even cooler by transferring the energy in the fridge into your kitchen (which is, hopefully, much warmer than the fridge or freezer).

For further details, you can read this article and these not-very-good Wikipedia articles: Heat Pumps, Air Source Heat Pumps. And at this point, my facts become an amalgamation of things I have read and things I have learned in conversation — sorry about the lack of citations.

Some trade-offs

Heat pumps are fairly rare in the US today. They are more common internationally (the system we are going with is from Mitsubishi), and the systems have been around for a while. They are common enough, and becoming more popular as their efficiency is recognized, that we shouldn't have problems maintaining our system, but it is a risk.

Heat pumps, at least the ones we are considering, are driven electrically, but run at a much higher efficiency than electric baseboard heat. They are more comparable to an efficient gas furnace, but as the opening question points toward, heat pump systems are easier to configure into zones. Separately-controlled and conditioned zones are often more efficient since you aren't heating the whole house to the same level, but just the area(s) you are currently using. The Mitsubishi system provides a number of other efficiency features, such as providing a variable amount of conditioning (instead of full-on or full-off), and less heat loss in the small, well-insulated refrigerant lines versus standard ductwork.

Heat pumps require refrigerant, and refrigerants are a negative, as far as the environment is concerned. This is partially mitigated by fact that this is a long lifetime, closed system. Mitsubishi also uses refrigerant that has a low environmental impact.

Some heat pump systems, including the one we are using, are reversible — they can transfer energy in  and act as a heater or transfer energy out and act as an air conditioner. Even though we were not planning on installing an air conditioning unit at construction time, using a system which supports both functions results in a simpler, more cost efficient solution.

No ducts! The refrigerant line is hardly larger
than the wiring, and with the wrapping
it's still ~2" in diameter

Heat pumps have one more really big advantage for a green home: they don't require ducts. We are going with a fully ductless setup where the refrigerant lines run directly from the exterior units to the distribution units. This allowed us to open up the main floor by removing the need for some interior soffits. The impact on the roof was much more substantial. Because we don't need to run ducts, our home is now able to support a roof design that provides a significantly higher level of insulation. Since the roof is one of the large energy leakers in a standard home, this will result in a much tighter home. (Sneak preview: this ended up having some unintended consequences in our kitchen.)

Our system

We are going with a Mitsubishi heat pump system. Two external heat pump units will drive six interior distribution units, for a total of six different zones (one per bedroom, two on the main floor, and one downstairs). We decided not to go with programmable thermostats since they are expensive and the units we are buying support a basic level of programmability — a single day/night cycle — that is good enough for us.

Not ugly, but not exactly beautiful

This is one of the units (installed over the door of our dressing room). The units are not huge, but they are not small either. Each unit is about the width of a doorway, and about a foot tall and a foot deep. This is fine in the bedrooms and media room, where we were able to put them in fairly out-of-the-way locations (over doorways). However, we were not able to do this in the open living area of the main floor; we put the distribution unit behind the fireplace — okay, but not ideal.

This was actually a bit of a disappointment. We initially planned to do a system that used small ducts on the main floor to move the air from the distribution units to the open space. This is when green politics got involved. We're going for a Built Green certification on our home — this is a nice-to-have that gives us a verification that our home is green by some external standard and is also good marketing fodder for our builder. To get a Built Greet certification, your heating system must be Energy Star approved. However, Energy Star does not handle configurable systems well.

The exterior hookup.
The installed unit will only be 3' x 3' with a depth of 1'

Both the ducted and ductless variants of the Mitsubishi are Energy Star approved. However, what is not approved is having a single exterior unit drive one ducted interior unit and one non-ducted interior unit. Energy Star approval applies only to the exact system that was evaluated. This makes sense — variations could potentially decrease the efficiency of a system. However, approval is binary, and there is no process for getting small variants approved; the variant has to go through the full approval process, and the cost of that is prohibitive for one-offs or all possible combinations. Okay, rant over =)

Overall, we're happy with the configuration that was installed. We'll provide an update once we've moved in and have experienced how this works in practice!

Review of Q1 2012

The first quarter of 2012 is over, and it was a quarter of great progress. It was the quarter of rough-in work.

Framing was completed:


Plumbing was added:


Then HVAC:


Fireplace:


And electrical:


Windows were installed:


And then siding:


The timelapse for the quarter shows all the exterior pieces coming together.


We spent a lot of time on design this quarter. Some of it was just-in-time design, such as the electrical and lighting. Framing changes were made based on 3D models of the interior. The master bath won't be installed for awhile, but the tiles need to be ordered now. There was a steady stream of small decisions, such as the fascia color for the roof trim. Many design discussions are ongoing as we take our high level design ideas and then refine the details as we gather samples, compare colors, and work through every individual piece.

The rough-in work is nearly done, and we are anxiously awaiting insulation and drywall. These will mark the beginning of the finish phase of the project. Each successive stage will appear to move at a slower pace, as more care is taken to perfect the details. Several areas may be in-progress at the same time, though. To accommodate this change, we will replace our weekly summaries with weekly overviews focusing on a single area. We'll go into details on individual elements, providing more background and design information, plus in-progress and final pictures of the installation. Our photo gallery and timelapse gallery will still be updated regularly with each weeks' progress.