Attic Space Research Articles

Effects of Attaching Baffles onto the Inclined Walls of Attic Frames for Purposes of Energy Conservation

This article addresses the buoyant air circulation inside attic spaces of houses and buildings with sloped roofs and horizontally suspended ceilings. In order to counteract the excessive heat transmission through the roof that takes place during the wintertime, when the attic is heated at the base, this study attached an array of baffles onto the top inclined walls to alter the flow characteristics of the buoyant air. To perform the computational analysis, the finite volume method is the vehicle for the discretization of the conservation equations. The Boussinesq approximation is not invoked, and all thermophysical properties are considered as temperature-dependent. Simulations are performed for several values of baffles length and the Rayleigh number. The influence of these parameters upon the flow and temperature patterns is analyzed and discussed. A comparison of the thermal performance between baffled attics and non-baffled attics is presented. The results show that the presence of baffles provides an important energy savings for heating and helps keep the attic at a desired temperature.

Numerical and experimental analysis of a passive room-dehumidifying system using the sorption property of a wooden attic space

In hot and humid tropical regions, air dehumidification is widely regarded as one of the keys to achieving a better indoor environment. This paper reports results for a passive room-dehumidifying system using an existing attic space as a chamber, wood as a desiccant material, and optimized ventilation and solar energy for system operation. Along with numerical calculations, field measurements were carried out in a test house in Japan over hot and humid summers in 2003 and 2004. It can be inferred that the wooden attic space alone had a relatively high dehumidification potential of 25 g/h m 2 of attic floor area. The fully operational system had relatively high dehumidification potential and could lower the humidity of a bedroom with an occupant by approximately 4–5 g/kg dry air during the night compared to natural ventilation. The electric coefficient of performance of the system was estimated as 15, compared with 3–5 for a typical commercial dehumidification system. Therefore, the system outlined in this study could represent a promising new passive tool for moisture control in hot and humid regions.

Turbulent natural convection in an air-filled isosceles triangular enclosure

This paper addresses turbulent natural convection of air confined in an isosceles triangular enclosure representing conventional attic spaces of houses and buildings with pitched roofs and horizontally suspended ceilings. The values to be considered are H = 0.86 m and 2.73 m for the height while the values 1.72 m and 5.46 m were assigned to the width, W, such as the aspect ratio H/ W remains 0.5. The third dimension of the cavity is considered long enough for the flow to be considered 2D. The base wall is heated at 20 °C and the inclined walls are cooled at 0 °C. This combination of factors leads to large Rayleigh numbers equal to 1.58 × 10 9 and 5 × 10 10. Turbulence is modeled by a low-Reynolds-number k– ε model. The system of governing equations, subject to the proper boundary conditions is solved with the finite volume method. Second-order-accurate QUICK and SIMPLE schemes were used for the discretization of the convective terms and the pressure–velocity coupling, respectively. The velocity and temperature distributions were calculated at different locations in the cavity and their mean quantities are presented. The local and average Nusselt numbers and the wall shear stresses are also presented. Since to the knowledge of the authors, no previous results on turbulent thermal convection in this geometry exist, the validation of the numerical code was performed by comparing velocity and temperature profiles against recent experimental measurements, obtained for a square cavity. Satisfactory agreement was observed.

Benefits Derivable from Connecting the Bottom and Top Walls of Attic Enclosures with Insulated Vertical Side Walls

ABSTRACT This article addresses buoyant air circulation inside attic spaces of houses and buildings with sloped roofs and horizontally suspended ceilings. Depending on the season of the year, two different heating/cooling scenarios may occur. In order to counteract the excessive heat transmission that takes place during the winter and summer seasons, heavily insulated, vertical side walls of variable height h are placed at the hot/cold intersection between the active walls. As a result, the shape of the enclosure switches from an isosceles triangular enclosure to a trapezoidal enclosure, but having two insulated side walls. The finite-volume method is employed to perform the numerical computations.

Field Performance of Unvented Cathedralized (UC) Attics in the USA

This article reports on field experience of unvented cathedralized (UC) attics in several environments in the United States. Traditionally, in some regions of the country, because of high water tables or the risk of flash flooding and lower cost, slab on grade construction is a preferred mode of construction. Mechanical equipment for air conditioning and distribution ducts are usually located in the attic spaces to conserve space. Conventional construction involves providing insulation on the floor of the attic and venting the attic space to the outside. The loss in efficiency in operation of the equipment and through duct leakage is no longer sustainable. Insulating the attic roof itself and blocking of ventilation to the outside transfers the air and thermal energy controls from the boundary with the living space to the plane of the roof. The air distribution systems now fall within conditioned space, which increases their efficiency, durability, and maintainability. While design criteria vary for different climatic regions, UC attics can be insulated in various ways and by using different vapor diffusion resistance strategies of the roof assemblies depending on the climate. The field data presented in this article include measured temperature of asphalt shingles, and thermal and moisture conditions of attic spaces and roof sheathing, as well as air leakage rates. This is of interest for determining probable roofing durability. A more complete understanding of the hygrothermal performance of the assemblies was gained through these measurements.

Utilizing Latent Building Thermal Mass for Dehumidification

Traditionally, attic space in buildings is perceived as a source of nuisance. In winter, moisture condensation on the attic ceiling encourages mildew growth. In summer, the heat buildup in the attic space increases the cooling load. However, if the attic is integrated in a holistic design and control strategy, it can function as a solar energy collector, a heat exchanger, and a desiccant. This research investigates energy saving by optimizing direct and indirect ventilation through the attic to precool buildings and to reduce humidity. The proposed energy saving strategies are examined in a double story house with an attic. The house is located in a moderate-humid climate. The built-up heat in the attic space and outside air ventilation is used to dry up roof construction materials during the day. When outside air cools down during the night but maintains high humidity, the indoor air is circulated through the attic space. The attic construction materials absorb moisture from the indoor air. Thus, indoor air loses both heat and moisture. EnergyPlus Simulation software was used to simulate these cooling and dehumidification strategies. The simulation results show a significant passive cooling and dehumidification in the building.

Numerical computation of buoyant airflows confined to attic spaces under opposing hot and cold wall conditions

The present paper addresses laminar natural convection of air confined to an isosceles triangular cavity representative of conventional attic spaces in houses and buildings with pitched roofs and horizontal suspended ceilings. Detailed experimental data in terms of velocities, temperatures and wall heat fluxes has become available for attic spaces under summer and winter conditions some time ago. However, the comparison between the numerical-obtained temperatures and mean wall heat fluxes against the experimental-measurements is still lacking in the specialized literature. Two relevant cases of isosceles triangular cavities are considered: case 1, the base is cooled and the two inclined walls are symmetrically heated and case 2, the bottom base is heated and the two top inclined walls are symmetrically cooled. To perform the computational analysis, the finite volume method is the vehicle for the discretization of the conservation equations. The Boussinesqian fluid approximation is not invoked and all thermophysical properties are taken as temperature-dependent. Most numerical simulations have assumed the existence of a vertical plane of symmetry passing through the middle of the isosceles triangular cavity in order to deal with a manageable computational domain in the form of a right-angled triangle that is half the size of the isosceles triangular cavity. However, the computational domain adopted in this work has been taken as coincident with the physical domain. Overall, the numerical predictions of velocity, temperature and mean wall heat fluxes match reasonably well with the experimental measurements for the two cases under study here.

EXPERIMENTAL-BASED CORRELATIONS FOR THE CHARACTERIZATION OF FREE CONVECTION OF AIR INSIDE ISOSCELES TRIANGULAR CAVITIES WITH VARIABLE APEX ANGLES

The archival literature contains an abundance of correlations for the characterization of laminar-free convection in rectangular, square, and annular cavities, but unfortunately does not disclose a single correlation for triangular cavities. A prominent application of triangular cavities specialized to isosceles shapes arises in air-filled attic spaces of houses and buildings with sloped roofs and horizontal suspended ceilings. In this work, two contrasting situations are considered embodying three apex angles and several Grashof numbers: a hot base and symmetrically cold inclined sides for winter conditions, and a cold base and symmetrically hot inclined sides for summer conditions. The goal of this article is to construct two dependable correlations, one for the mean convective coefficient at the air/wall interface, and the other for the temperature variation of the ascending air along the center plane of attic spaces. The input data was taken from precise measurements available in the specialized literature.

The Composition of Hedonic Pricing Models

A house is made up of many characteristics, all of which may affect its value. Hedonic regression analysis is typically used to estimate the marginal contribution of these individual characteristics. This study provides a review of recent studies that have used hedonic modeling to estimate house prices. The findings indicate that slanted versus flat roof, sprinkler system, garden bath, separate shower stall, double oven and gated community positively affect selling price while not having attic space, living in an earthquake zone, proximity to a hog farm, proximity to a landfill, proximity to high voltage lines, corporate-owned properties, percentage of Blacks or Hispanics in an area and properties that require flood insurance negatively affect selling price.

Middle ear cholesteatomas in temporal bones with low middle fossa tegmen

Temporal bone with low middle fossa tegmen is one of the causative factors of troublesome complications in cholesteatoma patients.One hundred and thirty-five consecutive patients with acquired cholesteatoma, who visited Mitsui Memorial Hospital between 1993 and 2004 for ear surgery, were studied with a retrospective case series study design (75 males and 60 females, age ranging from 12 to 75 years old (mean 49), total 144 ears: 105 attic type and 39 pars tensa type).Thirteeen cases were with low middle fossa tegmen, 33 cases had inner ear fistula, and facial nerve exposure was seen in 23 cases. Although there was no statistically significant difference compared to cases with normal attic space, the risk of complications was twice as high in cases with low middle fossa tegmen: inner ear fistula was seen in 38% (5/13 ears) and facial nerve exposure was seen in 31% (4/13 ears). We conclude that extra attention and fine procedure are necessary in mastoidectomy in such cases.

Suitable roof constructions for warm climates—Gazimağusa case

This research aims to find the suitable roof constructions for warm climates. The research has been carried out at Gazimağusa, North Cyprus. With the limited research budget 14 different roof constructions were selected and tested on a test house. These constructions included the types which are widely used in Cyprus and also the new ones. The roof constructions were tested under continuously air-conditioned and non-acclimatised regimes. They were also tested for the risk of condensation. Most of the research on similar aspects were done in terms of energy loss and gain. This research has been designed to study the roof constructions in terms of thermal comfort of the users. Naturally, the roof constructions which have the highest thermal resistance will result in lowest heat gain and loose. In this study instead of finding the roof constructions which gain the least amount of heat during the hottest days of summer or the ones which loose the least amount of heat during the coldest days of winter, it was aimed to find how much they provide thermal comfort throughout the year. In this respect, the roofs with thermal insulation showed the best performance. The location of the thermal insulation materials towards the inner surface of the section increased the performance. Inclined timber roof constructions on reinforced concrete ceiling save the buildings from solar bombarding in summer. However, to prevent the humidity accumulated, the attic space should be very well ventilated. On flat roofs, not only the thermal resistance of the roof section, but also the light reflectance of outside surface materials effected the thermal performance. Outside surface materials with very high light reflectance reduced heat gain in summer considerably. In buildings which are air conditioned in summer, there is condensation risk. The defects due to this condensation can be avoided by the use of thermal insulation materials which are not effected from water. There is also condensation risk for winter. However, it was found that this condensation can dry if the building is ventilated.

庄内地方の中門型農村住宅の変容過程 : 屋根裏空間と中門形態の変容

The purpose of this study is to explore the changing process of attic space and "CHUMON" type, examining room layout, structure, and dwelling space of farmhouses in Shonai district. First, attic space was all storage space, and in the Middle of Meiji, the mezzanine was produced taking advantage of the difference of ceiling height. In the early stages of Showa, the upper story of the whole first story became storage space in mezzanine, and the house which had dwelling space parts of mezzanine also appeared. And it changed to dwelling space of perfect second story type after the Showa 40s. Next, traditional "CHUMON" type changed to the mezzanine type in "CHUMON" because of changing clay tile roofing from reed roofing in the early stages of Showa. Furthermore, it changed to "GENKAN-CHUMON" of perfect second story type after the Showa 40s.

Cellulosic building insulation versus mineral wool, fiberglass or perlite: installer's exposure by inhalation of fibers, dust, endotoxin and fire-retardant additives.

A task-specific exposure matrix was designed for workers installing building insulation materials. A priori, a matrix element was defined by type of task (installer or helper), type of work area (attic spaces or wall cavities) and type of insulation material (slabs from mineral wool, fiberglass or flax; loose-fill cellulosic material or perlite). In the laboratory a mock-up (full scale) of a one-family house was used for simulated installation of insulation materials (four replicates per matrix element). Personal exposure to dust and fibers was measured. The dust was analyzed for content of endotoxin and some trace elements (boron and aluminum) from fire-retardant or mold-resistant additives. Fibers were characterized as WHO fibers or non-WHO fibers. In support of the exposure matrix, the dustiness of all the materials was measured in a rotating drum tester. For installers in attic spaces, risk of exposure was low for inhalation of dust and WHO fibers from slab materials of mineral wool or fiberglass. Slab materials from flax may cause high risk of exposure to endotoxin. The risk of exposure by inhalation of dust from loose-fill materials was high for installers in attic spaces and for some of the materials risk of exposure was high for boron and aluminum. Exposure by inhalation of cellulosic WHO fibers was high but little is known about the health effects and a risk assessment is not possible. For the insulation of walls, the risk of installers' exposure by inhalation of dust and fibers was low for the slab materials, while a high risk was observed for loose-fill materials. The exposure to WHO fibers was positively correlated to the dust exposure. A dust level of 6.1 mg/m3 was shown to be useful as a proxy for screening exposure to WHO fibers in excess of 10(6) fibers/m3. In the rotating drum, slabs of insulation material from mineral wool or fiberglass were tested as not dusty. Cellulosic loose-fill materials were tested as very dusty, and perlite proved to be extremely dusty.

Heat exchange in an attic space

Thermal effects in building attics are extremely important in regions where temperature extremes occur regularly. In particular, in the northern regions of North America, cold winters can lead to a dangerous build-up of ice on roofs, as well as preventing heat being distributed efficiently through the building. This paper examines heat transfer within attics and looks at an inexpensive solution technique involving ceiling fans. The computer model developed accurately reproduces the results of previous investigations, presents solutions for realistic Grashof numbers, and demonstrates the effects of installing ceiling fans in the ceilings of top storey rooms in affected buildings.

초기 중이 진주종의 치료

Chronic otitis media with cholosteatoma had been one of the most prevalent forms of otological disease. However, recently, the incidence of chronic otitis media have decreased owing to better economic status and health care. Thus, cases of middle ear surgery have also decreased relatively in number. So it seems that otologists nowadays should be engaged in revision surgery of the middle ear and management of early cholesteatoma. While the incidence of extensive or complicated cholesteatoma has dramatically decreased for last decades, the early staged or less extensive cholesteatoma and retraction pockets are more frequently found. Especially localized adhesive otitis media, usually posterior tympanic membrane, is one of the most difficult dilemmas for the otologist. There are several controversial issues for managing patients with early cholesteatoma : 1 ) conservative care or surgical treatment 2) techniques of surgery 3) whether or not mastoidectomy. So surgery for early cholesteatoma is thought to be reconstructive rather than destructive and it can be a prophylactic operation. I proposed a strategy for the management of early cholesteatoma which was based on safe marsupialization of retraction pocket or cholesteatoma, preservation of the mucosa, adequate ventilation, and prevention of retraction pocket. In case of attic retraction pocket or cholesteatoma, atticotomy with scutumplasty was made. On the other hand, the procedure to remove posterior annular bone and posterior scutum to allow access tympanic sinus and posterior attic space designated as posterior sinusectomy with reconstruction were applied to sinus retraction pocket or cholesteatoma. Early tensa retraction cholesteatoma would be managed as the combination of atticotomy and posterior sinusectomy. So I preferred the term “atticosinoplasty” which includes attic reconstruction with scutumplasty after atticotomy and posterior sinusectomy. If the disease seems to extend to mastoid, endoscopes were introduced transmeatally. If cholesteatoma occupies in mastoid, complete mastoidectomy is made, and sometimes mastoid cavity is obliterated to eliminate the cavity problems. During the last 7 years, I managed surgically 208 cases of attic or sinus cholesteatoma, so-called early cholesteatoma, among which there were 45 cases of atticosinoplasty. I analysed 45 cases with atticosinoplasty with special reference to period of postoperative care and hearing result, as compared to cases with mastoid obliteration and open cavity mastoidectomy. In conclusion, I personally think that middle ear cholesteatoma has a possibility of different clinical entity rather than a kind of chronic otitis media, eustachion tube dysfunction can not be always a prerequisite of middle ear cholesteatoma but it can be a secondary phenomenon, and finally surgury for early cholesteatoma is reconstructive rather than destructive ant it can be a prophylactic operation. (J Clinical Otolaryngol 2002;13:13–19)

Canal-down mastoidectomy: experience in 81 cases.

To identify the common presentation(s) and the clinical and operative finding(s) in patients with cholesteatomatous and long-term noncholesteatomatous chronic suppurative otitis media and to adapt a surgical management best suited to ensure long-term safety in these Papua New Guinean patients for whom postoperative follow-up is minimal. Retrospective case series. Port Moresby General Hospital, the tertiary referral center for otolaryngologic services. Eighty-one patients in all age groups who received a clinical diagnosis of chronic suppurative otitis media, with or without cholesteatoma, with or without its associated complications. Canal-down (modified radical) mastoidectomy with wide meatoplasty. Adults were more commonly affected than adolescent or pediatric cases, and there was a male preponderance. The median age was 24 years (range, 13 months to 73 years). Otorrhea remained the most common presentation in all age groups. Postauricular abscesses and fistulae were seen frequently. Cholesteatoma and granulation with polypoidal mucosa were frequent operative findings; a high incidence involved both the attic space and the antrum. Five (6%) patients had preoperative facial paralysis; in addition, postoperative facial paralysis developed in three (4%) patients. The incidence of postoperative "wet ear" was high in all age groups. Meningitis was the most common intracranial complication, followed by lateral sinus thrombosis. There were seven (9%) deaths altogether, and all the deaths occurred as a direct result of otogenic intracranial complication. Lack of health consciousness, poor socioeconomic status, and lack of health care delivery system resulted in late presentations and poor postoperative follow-up. Hence, the canal-wall-down technique with wide meatoplasty is recommended to ensure a best possible one-time treatment in Papua New Guinean patients with cholesteatomatous or long-term "dangerous" chronic suppurative otitis media with or without complications.

Return Air Leakage Impact on Air Conditioner Performance in Humid Climates

An experimental study was conducted to quantify the effect of return air leakage from hot/humid attic spaces on the performance of a residential air conditioner. Tests were conducted in psychrometric facilities where temperatures and humidities could be controlled closely. The test air conditioner had a nominal cooling capacity of 12.3 kW and a seasonal coefficient of performance of 3.8. Return air leakage from hot attic spaces was simulated by assuming adiabatic mixing of the indoor air at normal conditions with the attic air at high temperatures. Effective capacity and coefficient of performance both decreased with increased return air leakage, leakage air temperature, and air humidity. Under attic conditions of 54.4°C and 20 percent relative humidity, 10% return leakage reduced the effective cooling capacity and coefficient of performance of the air conditioner by approximately 30%. Power consumption was relatively constant for all variables except outdoor temperature. The sensible heat ratio (SHR), which is a measure of the dehumidification performance, increased with increasing leakage.

Natural Convection in a Trapezoidal Enclosure with Offset Baffles

A numerical investigation has been made of natural convection heat transfer in a trapezoidal enclosure (representing attic spaces) with offset baffles. Two thermal boundary conditions representing summerlike conditions (upper surface heated) and winterlike conditions (upper surface cooled) and two baffle heights are studied. For each boundary condition and baffle height, two baffle positions are considered. In position I, the upper baffle is offset toward the heated vertical wall and the lower baffle is offset toward the symmetry plane of the enclosure, whereas in position II, the upper baffle is offset toward the symmetry plane and the lower baffle is offset toward the heated wall. Rayleigh number values range from 10 3 to 5 × 10 7 for summerlike conditions and from 10 3 to 10 6 for winterlike conditions. Predictions reveal a decrease in heat transfer in the presence of baffles. In winterlike conditions, convection starts to dominate at a Rayleigh number much lower than that in summerlike conditions. The maximum reduction in heat transfer is achieved with long baffles placed in position II for summerlike conditions and in position I for winterlike conditions. Average Nusselt number correlation for both boundary conditions are presented.

NATURAL CONVECTION IN TRAPEZOIDAL CAVITIES WITH BAFFLES MOUNTED ON THE UPPER INCLINED SURFACES

A numerical investigation has been undertaken to study the effects of mounting baffles to the upper inclined planes of trapezoidal cavities (representing a building or attic space). Two thermal boundary conditions are considered: (a) the vertical and upper surfaces are heated while the lower surface is cooled (summerlike conditions); (b) the lower surface is heated while the other surfaces are cooled (winterlike conditions). For each boundary condition, computations are performed for two baffle heights and two baffle locations. Rayleigh number (Ra) values range from 103 to 5 x 107 for summerlike conditions and from 103 to 106 for winterlike conditions. For both boundary conditions, results obtained with air as the working fluid reveal a decrease in heat transfer in the presence of baffles. In winterlike conditions, convection starts to dominate at an Ra much lower than that in summerlike conditions. The decrease in heat transfer becomes increasingly more significant as the baffle gets closer to the heated vertical wall for the bottom-cooled situation and as the baffle gets closer to the symmetry line for the bottom-heated case. In general, this decrease in heat transfer is higher with taller baffles. Average Nusselt number (Nu) correlations for both boundary conditions are presented.

Numerical Heat Transfer Attic Model Using a Radiant Barrier System

A two-dimensional, steady-state finite-element model was developed to simulate the thermal effects of the application of an attic radiant barrier system (ARBS) inside a ventilated residential attic. The attic is ventilated using the exhaust air from an evaporative cooler. The study uses a k-ε turbulent model to describe the velocity and temperature distributions in the attic. The ambient temperature and solar isolation densities on the outside inclined attic surfaces are used as driving functions for the model. The model also included the appropriate heat exchange modes of convection and radiation on these outside surfaces. Several recirculation zones were visually observed in the attic flow pattern. Also, the use of the ARBS seems to lower the heat transfer through the ceiling by 25–30%, but this effect decreases significantly as the outside ventilation rates are increased through the attic space. The 2D model revealed some interesting temperature distributions along the attic surfaces that could not have been predicted by the one-dimensional models. The lower emissivity ARBS seems to raise the temperature of the inclined attic surfaces as well as the temperature of the exhausted ventilation air.