For years, the question posed in the title wasn’t heavily considered. Vented roofs were the standard, and unvented roofs were practically unheard of. Unvented roofs have become more popular in recent years for a wide variety of reasons, many of which we’ll examine in the body of the article. Before getting into the meat of Read more
For years, the question posed in the title wasn’t heavily considered. Vented roofs were the standard, and unvented roofs were practically unheard of. Unvented roofs have become more popular in recent years for a wide variety of reasons, many of which we’ll examine in the body of the article.
Before getting into the meat of things, it’s worth noting that “what is the best design?” never has a clean answer; if it did, things would be a lot less interesting. Instead, what we’re considering is the advantages of both roofing types given certain circumstances. In other words, vented roofs may well be the best design for one home, while an unvented roof will be a better solution for another home.
Vented roofs serve a number of different purposes and their roles vary from climate to climate. In colder climates, the main purpose of a vented roof is to keep the roof cold and reduce the formation of ice dams. A secondary goal is to vent moisture that infiltrates the attic from the conditioned home. In warm climates, ventilation serves to reduce the cooling load of the rest of the building by reducing the impact of solar heating, though studies have shown this method isn’t as effective as we previously thought.
There are a couple of disadvantages to vented roofs; they tend to be more susceptible to certain hazards. Windstorms, for example, can cause vented soffits to collapse, creating excessive pressure which may lead to window blowout and roof loss.
Unvented roofs have a number of advantages. Ventilation becomes more difficult the more complicated a roof’s construction is. As a result, unvented roofs have become popular in homes with feature-dense roofs – think multiple skylights, dormers, and other aesthetic flourishes.
The disadvantages of unvented roofs have, to a certain degree, been overstated – in hot climates, the extra heat gain from unvented roofs rarely exceeds a couple of degrees Celsius.
Moisture from the conditioned section of the building must be addressed when using an unvented model. Generally, this can be handled by employing moisture barriers during the construction process, effectively creating something of a self drying roof. The folks at Quik-Therm Insulation say you can employ permeable insulation because “a self-drying non-vented roof design is unattainable if the roof assembly can’t dry both inward and outward”.
Roofing and HVAC
There are a number of reasons why you might want to install ductwork and mechanical systems in the attic of a home, including aesthetic considerations and saving space. In light of this, it’s important to think about the difference between vented and unvented roofs and different HVAC configurations.
When ductwork and mechanical systems are located in the roof, an unvented roof is generally preferred. When the roof is vented, exfiltration from leaky ducts and air handling units is intensified, and infiltration from the external climate is accelerated by the change in pressure from air loss. This creates thermal penalties in both hot and cold climates. What’s more, heat leaking from ducts can melt snow and create ice dams, the prevention of which is one of the key reasons to employ vented roofs in the first place.
There is much debate about whether or not HVAC systems should ever be placed in the attic. Many modern green building principles rely on a completely sealed building envelope to avoid hot and cold spots caused by increased thermal transfer. The attic and roof can play an essential role in building envelope construction; sealing the roof off from the rest of the house can allow the creation of a highly insulated barrier to the conditioned areas of the home.
Should you opt to run ductwork or place mechanical systems in the attic, an unvented roof is best for avoiding thermal penalties as the ductwork will be located in a conditioned space, allowing the system to recover thermal losses through the ducts. As Provincial Heating points out, any weakness in your thermal envelope can cause problems: “Wood studs between sheets of insulating fiberglass, for example, have a lower R-value and thus reduce the R-value of the total system”
As you can see, the best type of roof is highly variable. Are you in a cold climate with an uncomplicated roof? Is your HVAC system entirely located within the conditioned area of your house, and you want to use your attic as a thermal barrier? Your best bet is likely to be a vented roof.
Are you in a warmer climate? Is your roof difficult to construct? Do you want to keep ducts and the like in your attic? You’re probably better off with an unvented roof.
Keep in mind that vented and unvented roofs are quite different; everything from the building materials you use to the type of insulation you’ll install will vary depending on what type of roof you opt to construct. When advising clients on their HVAC systems, it’s important to consider the type of roof they have as well as their overall building envelope. Optimally, this should all be done during the planning and construction stages, but for replacements and renovations, roof type needs to be kept in mind.
Authors Bio: Kiara Fullam is a blogger and some of her favorite pieces can be found on Powertec Electric’s website.
As I sat watching the president’s recent press conference on the coronavirus, I listened to a health expert say that sunlight and humidity was a bad thing for this pesky virus. These two things can suppress and kill it. Earlier the same day, the governor of my fine state extended the stay-at-home order to the Read more
As I sat watching the president’s recent press conference on the coronavirus, I listened to a health expert say that sunlight and humidity was a bad thing for this pesky virus. These two things can suppress and kill it. Earlier the same day, the governor of my fine state extended the stay-at-home order to the end of May. I get confused easily, so stay at home but go outside? It’s not safe to be on a golf course or out with my family on a boat, but it’s okay to go shopping for flowers at a big box store with my family?
After weeks of hearing that masks were no deterrent to the virus, now the government is telling us that masks are a good thing. Where do we find these masks now? Most people I know are now making their own and wearing these self-made fabrics when out in groups. Social distancing up to 13 ft., wearing masks in public groups of six to 10 (i.e. supermarkets), proper handwashing, etc., are all effective ways to prevent the spread.
But here’s the thing: After more than a month of being cooped up indoors, I could see this coming from a mile away—people are getting restless. Half want the country to gradually reopen, now. The other half wants to heed the advice of scientists. And there are those that still think this is a hoax, or not that big a deal as portrayed by the “fake media.” The early retort was, “Do you even know anyone that has this disease?” Actually, I do. A few neighbors and a good contractor friend of mine had it. He is healthy, and he said it kicked his ass for the better part of 10 days. He had never experienced an illness like that.
While I tire of hearing of “bending the curve” or “flattening the curve,” especially in my state where we still are hearing about thousands of new cases per day, from what I understand, the shelter in place order is really about keeping the hospitals from becoming inundated with incoming patients. But the “Why can’t the immune-compromised and elderly stay home and let those ‘healthy’ people return to their normal lives” discussions have dominated some circles. Yet the caution here is that people who have it can be asymptomatic for a few days before showing symptoms and could be carriers unknowingly. Again, the dilemma. What to do? What to do?
But, you see, we Americans can be spoiled. You can’t infringe upon our constitutional rights and civil liberties. I can’t say I completely disagree with this. The collapse of the U.S.—and global—economy could have more lasting detrimental effects on families, jobs and mental well-being.
Nevertheless, huge props go out to all of the healthcare workers, first responders, grocery store employees, all of those who still get after it daily. We work in an industry where tradespeople are considered essential, and they continue to go to work every day. Yet, most contractors and service techs tell me they don’t need the accolades, they just want to do their job, and do it well, and safely, of course. Some contractors are adjusting by wearing facial coverings—masks and eyewear—and practicing safe social distancing to keep themselves safe and give the customer peace of mind. Supply houses are adjusting protocols to offer curbside or parking lot pick-ups or letting a few people in the building at a time.
My hope is that we find a cure or some mixture of drug therapies that, if we contract the virus, there’s a very good chance we won’t die if we take the drugs. I’ve been reading success stories regarding plasma infusions that contain the corona antibody, an Ebola drug Remdesivir, and the malaria drug, hydroxychloroquine. All have shown promise in some cases, but potentially deadly—or with debilitating side effects—in others. Some of these controlled trials may take months to fully understand the efficacy, or to issue as an FDA-approved drug therapy.
And another thing. I keep hearing about not enough ventilators: Hospitals are running low on ventilators to help keep people alive. However, in a recent report, nearly all COVID-19 patients put on ventilators in New York’s largest health system died. In fact, a friend of mine recently wrote a piece from the University of Chicago that shows “remarkable” success using ventilator alternatives as a way to treat critical care patients. Something to think about. (https://www.uchicagomedicine.org/forefront/coronavirus-disease-covid-19/uchicago-medicine-doctors-see-truly-remarkable-success-using-ventilator-alternatives-to-treat-covid19)
All signs point to a vaccine as the only way to fully get past this. I recently saw a headline that read “Vaccine Coming Soon.” When I clicked on the story, it mentioned that the vaccine will be here by next spring. SOON?! There will be rioting in the streets if progress isn’t made as early as this summer—or at least opening up the economy in gated stages, which in some parts of the country are starting to implement.
How the world has changed over these past few months. So, where do we go from here? That’s the question we all have been asking ourselves. Information, misinformation, rumors, fake media, etc. all can play into education, and fear. I’ll continue to maintain safe and healthy procedures, heed the advice of people that know more than I do, and always support and commend those that are going above and beyond.
I will always preach that a successful cast iron water boiler installation begins with proper planning. I worked for an oil company for 20 long years, and nine years of that I was a service manager. During this time, I came across many problematic jobsites. I would evaluate the installation issues and try to figure Read more
I will always preach that a successful cast iron water boiler installation begins with proper planning. I worked for an oil company for 20 long years, and nine years of that I was a service manager. During this time, I came across many problematic jobsites. I would evaluate the installation issues and try to figure out where the problems had started. This knowledge has greatly helped me as a Training Manager for U.S. Boiler Company. Now, after 40 years in the heating business, I know how important proper boiler installation planning really is for reducing the number of problem jobs and expensive callbacks. In fact, planning is much easier than you may think …
- Proper boiler sizing. Complete a thorough heat loss calculation. Do not fall into the trap of oversizing the boiler because you sized it based on the old boiler size or you measured the connected radiation load, and never allow the customer to talk you into a larger boiler than needed. Today, with physically smaller boilers and less water volume, oversized boilers will short cycle more than ever. Increased short cycling means higher maintenance, higher fuel costs, and higher installation costs.
- Follow the boiler Installation & Operation (I&O) Manual. Be sure to follow one of the suggested near boiler piping options listed in the manual. The boiler tapping may not have to be the same size as the manifold piping. Use the flow charts for pipe size. You can pipe the boiler the same size as the tapping, or in some cases, use smaller piping dependent on the heat loss requirement. When the heat loss is known and the proper boiler size is chosen, you may be able to use smaller air separators, expansion tanks, and piping. You can use the following as a guide to size the boiler and system piping:
- 3/4” pipe = 40,000 BTU’s @ 4 – 5 GPM (gallons per minute)
- 1” pipe = 70,000 BTU’s @ 7 – 8 GPM
- 1-1/4” pipe = 160,000 BTU’s @ 16 – 18 GPM
- Bypass piping. Bypass piping is discussed briefly in the I&O manual. We cannot continue to install modern cast iron boilers the same way we used to install boilers with larger water volumes. When needed, a bypass system should be installed to protect the boiler. There are primary/secondary piping and circulated bypass options, both of which we will discuss later in this article.
The bypass system discussed in the manual is called a “boiler bypass” and is always installed the same size as the supply and return headers. When adjusted, the water flow through the boiler is slowed so the water spends more time in the boiler. This allows the boiler temperature to increase faster and decreases the possibility of boiler condensation. This means that some of the system return water is bypassed around the boiler and enters the supply beyond the boiler. I know what you are about to say. “Well, that will cool off the supply water going to the homes heating system!” That is correct, but it is not a problem. This is what I call a “poor man’s outdoor reset.”
The system will run quieter and the system water temperature will increase slowly until the radiation outputs enough heat to satisfy the thermostat. The colder it gets outside, the hotter the system supply water temperature will be. When the valve placement is installed as shown in the manual, we can easily adjust the ΔT through the boiler. Simply put, leave the bypass valve open and adjust the flow through the boiler with either valve located on supply or return pipes below the bypass pipe to slow the flow and force more water through the bypass. Partially close one of these valves and check the ΔT through the boiler. You will need a minimum of a 20°F rise. If this is a large water volume system, like cast iron radiation, increase the ΔT through the boiler to 35 – 40°F ΔT.
Quick Tip: If the bypass is hotter than the return pipe, the flow is backwards and you have piped a system bypass as opposed to a boiler bypass. Follow the piping in the manual to verify correct installation.
- Primary/secondary piping option. Primary/secondary piping utilizes hydraulic separation so that the water flow from system pumps do not affect boiler pump flow. This allows us to reduce the flow through the boiler to heat the water faster and heat the water to a higher temperature without affecting the flow in the system. In other words, we can have a higher flow in the system and a lower flow in the boiler. We still want a minimum of 20°F rise through the boiler, and for higher water volume systems we want a higher ΔT near 35°F – 40°F.
- Variable speed bypass pump option. To have the best boiler protection, install a variable speed bypass pump with a temperature sensor. This will change the speed of the pump to obtain the proper return water temperature. We offer a variable speed bypass kit with instructions for gas water boilers. This will protect the boiler in a high-water volume system or radiant in-floor radiation application.
Quick Note: My concern, and the reason for the above discussion of boiler protection from condensation, is excessive water flow through the boiler and slower temperature increase. I have experienced multiple boiler installations where the ΔT through the boiler is less than 20°F. In fact, I have witnessed some as low as 8°F. Lower ΔT’s are a result of excessive flow, possibly caused by the number or circulator sizes installed on the system. So, what is the minimum flow rate on cast iron water boilers? Look in the I&O manual under specifications and find the DOE heating capacity (MBH) of the boiler. For instance, the Series 3 model 304B has an input of 105k MBH and a DOE heating capacity of 88k MBH. Divide the DOE output by 10,000 to discover the maximum flow required by the boiler. If your flow exceeds that number, the ΔT will be less than 20°F. You can use this hydraulic formula to determine flow rate through the boiler.
- Avoid short cycling. Short cycling is caused by lower water flow, or higher ΔT. Higher ΔT may mean that the circulator is to small, the boiler is oversized, or the valves not adjusted properly. Generally, the minimum boiler flow should be half (but not limited to) of the maximum boiler flow.
Boiler Flow Formula:
Q/(500*ΔT) = Flow
Q = DOE Heating Capacity
Let’s put some numbers to that formula. Let’s assume that a boiler has a ΔT of 15°F. The Series 3 model 304 (referenced above) has a DOE heating capacity of 88,000.
88,000/10,000 = 8 GPM. This is the maximum flow required by the boiler. Divide this in half to get the minimum boiler flow. In this case, it would be 4 GPM.
Now, back to the formula.
ΔT = 15°F
88,000/(500 * 15) = Flow
88,000/7500 = 11.7 GPM
The flow is almost 4 GPM higher than the maximum flow the boiler should have. This tells us we need to achieve a 20°F ΔT, which means less flow through the boiler. Why do we have to much flow? There are oversized pumps or to many pumps. Using a bypass or primary/secondary strategy above, we can easily correct the flow through the boiler.
- Vent the boiler properly. If the boiler is chimney vented, the local and federal codes apply. A chimney liner may be required. If the unit is direct or power vented, the manufacturer dictates the venting according to the certifications obtained during testing. Since this article applies to cast iron water boilers, a sidewall vented boiler requires AL29-4C vent pipe. No plastic!
- Outdoor air. I like to use outdoor air as much as possible to verify enough combustion air. Plus, there is less chance of contaminated air.
- Gas pressure. Check the incoming gas pressure and the manifold (outlet) pressure with other gas appliances running. Check all safeties. Finally, always complete a combustion check.
Ron Beck is Outside Technical Advisor and Manager of Training for U.S. Boiler Company, where he’s been since 1998. Ron’s 34 years of experience in the heating industry include climbing the ranks of a HVAC company, from apprentice to service manager. Currently, he’s the go-to solution guy for contractors in the field.
Ron can be reached at RBeck@usboiler.net
Peter DeMarco, Executive Vice President of Advocacy and Research – The IAPMO Group In 2019, the World Health Organization (WHO) started monitoring the outbreak of a new coronavirus which ultimately was named COVID-19. The virus was first identified in Wuhan, China. This paper is intended to provide practical guidance for plumbing professionals who work on Read more
Peter DeMarco, Executive Vice President of Advocacy and Research – The IAPMO Group
In 2019, the World Health Organization (WHO) started monitoring the outbreak of a new coronavirus which ultimately was named COVID-19. The virus was first identified in Wuhan, China. This paper is intended to provide practical guidance for plumbing professionals who work on sanitary waste and sewer systems on how to protect themselves, their loved ones and their coworkers during the current pandemic.
Coronaviruses are so named because, when viewed under a microscope, they have protrusions that resemble a crown. They belong to a family of viruses common in both humans and many animal species. In rare occurrences, animal coronaviruses can mutate to the point where they are able to also infect humans, which is likely what occurred in China late last year. The potential for viruses that cross over from animals to humans to develop into an epidemic, happens when the virus can then be transmitted between humans. The COVID-19 virus is highly transmissible between humans and can cause respiratory illness and even death.
As of this writing on March 11, World Plumbing Day, the WHO has announced the outbreak qualifies as a pandemic, having spread on all inhabited continents. The worldwide number of humans diagnosed with COVID-19 has surpassed 120,000, with more than 4,300 deaths (see chart below). These numbers are predicted to grow. Unfortunately, there’s much we still don’t know about the virus, including important details about its transmissibility, how long it can survive on various surfaces or in water, and the range of illness severity amongst various population groups. It is known that the elderly and those who are immuno- compromised with pre-existing medical conditions are the most vulnerable for poor medical outcomes, which is consistent with other pathogen-based diseases, including influenza. However, contrary to some misinformation that’s currently available, the coronavirus is in fact considerably more dangerous than the current annual influenza virus.
So, what are the implications for those who work in the plumbing industry and what steps can plumbers take to stay safe? It is likely that the COVID-19 coronavirus can indeed be spread through building sanitary drainage systems. This became apparent when the Chinese government identified an outbreak in a Hong Kong high-rise building a few weeks ago (see the IAPMO white paper).
Therefore, for as long as the pandemic is still active, it should be assumed by anyone working on a sanitary drainage system that the virus is present. Considering the potential to come into contact with water and aerosols that contain the coronavirus when working on sanitary systems or sewers, it is highly recommended that plumbers wear proper personal protective equipment (PPE), including a full face shield that is worn over safety glasses, and gloves.
Of course, plumbers work on sanitary drainage systems that contain fecal matter and a host of dangerous pathogens every day. Taking careful precautions to prevent contact with wastewater and proper hand and arm hygiene is a matter of good practice for plumbers. In the United States, the Occupational Safety and Health Administration (OSHA) provides standards for worker protection. OSHA Standard 29 CFR 1926, Safety and Health Regulations for Construction provides the requirements for construction worker safety, including plumbers who work on sanitary drains, vent systems and sewers. The standards are available free at https://www.osha.gov/laws-regs/regulations/standardnumber/1926.
The most important subsections for plumbers to review are: 1926.20 – General safety and health provisions; 1926.21 – Safety training and education; 1926.22 – Recording and reporting of injuries; 1926.23 – First aid and medical attention; 1926.28 – Personal protective equipment; 1926.50 – Medical services and first aid; 1926.95 – Criteria for personal protective equipment; 1926.102 – Eye and face protection and 1926.103 – Respiratory protection.
Additionally, ASSE International’s Series 12000 Standard, Professional Qualifications Standard for Infection Control Risk Assessment for All Building Systems, is a standard that sets minimum criteria for the training and certification of pipe trades craftspeople, and other construction and maintenance personnel, on how to safely work in an environment with the potentially deadly diseases that may be present within
worksites. While the pandemic remains ongoing, ASSE International is making the ASSE Series 12000 Standard available for free at https://asse-plumbing.org/12000-2018 . The ASSE 12000 certification training addresses viruses, including the Sever Acute Respiratory Syndrome (SARS) virus, but does not specifically reference COVID-19. We welcome plumbers from across the globe to consider professional qualification for infection control risk assessment especially when working on sanitary systems that have a high probability of being contaminated with COVID-19, such as healthcare facilities and hospitals.
Finally, common sense still reigns supreme. Plumbers are advised to increase the frequency of hand washing and wash for at least 20 seconds with soap and water (even longer hand washing time is good practice after contact with wastewater); avoid touching of the face; cover any open cuts or wounds and wear proper PPE. If you personally come into close proximity, or into direct contact with an infected person, immediately report the incident to your supervisor and to your doctor or healthcare provider.
Good workplace and tool cleaning practices are also extremely important. Avoid sharing of tools with coworkers to the greatest extent possible. When choosing cleaning chemicals, look for cleaning agents with claims against viral pathogens. If such cleaning agents are not available, use soap and water and dry tools thoroughly after use. Keep your PPE clean as well by following manufacturer instructions carefully.
With no vaccine or treatment regimen currently available, it is important for all workers to be able to recognize the symptoms associated with contracting the coronavirus, which include fever, shortness of breath, and persistent cough. Symptoms can take between 2 to 14 days to become apparent after exposure to the virus. If you start to feel ill, stop work immediately so as to protect your coworkers and others around you, go home, contact your doctor and follow your doctor’s orders! This is critically important when working in a facility that houses immuno-compromised people.
The IAPMO Group sends its best wishes to plumbing professionals around the world. We hope that the information above is helpful. As usual, plumbers are on the front lines fighting the battles that keep people safe. By working carefully and thoughtfully, we can also keep ourselves and our loved ones safe as we deal with and defeat COVID-19!
Additional sources of useful information can be found at the links below:
Across the home improvement industry, public sentiment regarding wellness and overall health is at an all-time high. The average person has access to more information than ever before, as well as products and services that play an instrumental role in maintaining a healthy lifestyle. The HVAC industry is no exception to this shift in consumer Read more
Across the home improvement industry, public sentiment regarding wellness and overall health is at an all-time high. The average person has access to more information than ever before, as well as products and services that play an instrumental role in maintaining a healthy lifestyle.
The HVAC industry is no exception to this shift in consumer sentiment, as homeowners demand HVAC solutions that not only are efficient and cost effective but also play a key part in ensuring a healthier indoor environment. Homeowners want to know their HVAC system is improving their indoor air quality, as they gain understanding of the connection between air quality and health.
This is where an HVAC professional can help explain the importance of a right-sized HVAC system equipped to provide quality airflow, indoor humidity management, and air filtration regardless of the season or climate.
The emerging healthy homes trend represents a huge opportunity for HVAC professionals who have access to complete comfort and air quality solutions. There is a unique opportunity to explain how a healthier home is possible with an efficient HVAC system that filters small particulates in the 2.5-micron range out of the air, and monitors and controls humidity levels across the whole home. Small particles in this size range will escape basic filters and may be inhaled by occupants in the home, negatively affecting health.
When it comes to indoor humidity, very dry conditions can be problematic for one’s health and comfort and on the contrary, high humidity poses comfort and mold-growth risks as well. Dealers should walk homeowners through the process of why maintaining a happy medium (30-50% indoor relative humidity) is critical.
Highlighting the importance of improving a home’s indoor air quality opens the door to selling additional solutions to customers. The conversations are evolving beyond just the heating and cooling equipment, and instead educating homeowners in a way that points him or her in the direction of a healthier home.
Ideally, what an HVAC professional should focus on when selling a solution is arming their customers with the right information to ensure a healthier indoor environment. In doing so, homeowners will organically recognize the critical nature of an HVAC solution that considers their own health and wellness. Additionally, the HVAC professional can position themselves within the customer’s inner circle of trust by not pushing the sale, but instead learning about the homeowner and addressing the problems that can be solved with the right HVAC solution.
Over the next year, the healthier home trend is expected to grow and will continue playing a major role in the HVAC solutions that dealers can provide. This trend brings together the HVAC professionals and others in the home improvement and building ecosystem to inform and assist customers in creating a home with the best indoor air quality.
We can expect to see all players across the housing industry come together to set goals, talk about challenges, and ultimately deliver on a house that’s more comfortable, efficient, and healthier in order to serve this growing consumer demand. We’re looking forward to helping drive this innovation forward and help our HVAC professionals understand the key role they play in educating homeowners about the importance of indoor air quality and creating a healthier home.
Mike Topitzhofer is the National Business Development Manager – Building Science for American Standard. As a building science advocate through the HVAC manufacturer, he works to increase energy efficiency, comfort, long term durability and IAQ in homes.